Добірка наукової літератури з теми "Page Walk Caches"

In a large multiprocessor server platform using multicore chips, the scheduler often migrates a thread or process, in order to achieve better load balancing or ensure fairness among competing scheduling entities. Each migration incurs a severe performance impact from the loss of cache and Translation Lookaside Buffer (TLB) footprints and subsequent higher cache misses and page walks. Such impact is likely to be more severe in virtualized environments, where high over-subscription of CPUs is very common for server consolidation workloads or virtual desktop infrastructure deployment, causing frequent migrations and context switches. We demonstrate the performance benefit of preserving a portion of L2 cache—in particular, MRU cache lines—and warming the destination L2 cache by prefetching those cache lines under different migration scenarios. We observed a 1.5-27% reduction in CPI (cycles per instruction) following a migration. We also study the effectiveness of preserving TLB entries over a context switch or migration.

In Victorian times, when female travel narratives were read as excursions rather than expeditions, it was common for women authors to preface their travels with an apology. “What this book wants,” begins Mary Kingsley’s Travels in West Africa, “is not a simple preface but an apology, and a very brilliant and convincing one at that” (4). This tendency of the woman writer to depreciate her travel with an acknowledgment of its presumptuousness crafted her apology essentially as an admission of guilt. “Where I have offered my opinions,” Isabella Bird writes in The Englishwoman in America, “I have done so with extreme diffidence, giving impressions rather than conclusions” (2). While Elizabeth Howells has since argued the apologetic preface was in fact an opposing strategy that allowed women writers to assert their authority by averting it, it is certainly telling of the time and genre that a female writer could only defend her work by first excusing it. The personal apology may have emerged as the natural response to social restrictions but it has not been without consequence for female travel. The female position, often constructed as communal, is still problematised in contemporary travel texts. While there has been a traceable shift from apology to affirmation since the first women travellers abandoned their embroidery, it seems some sense of lingering culpability still remains. In many ways, the modern female traveller, like the early lady traveller, is still a displaced woman. She still sets out cautiously, guide book in hand. Often she writes, like the female confessant, in an attempt to recover what Virginia Woolf calls “the lives of the obscure”: those found locked in old diaries, stuffed away in old drawers or simply unrecorded (44). Often she speaks insistently of the abstract things which Kingsley, ironically, wrote so easily and extensively about. She is, however, even when writing from within the confines of her own home, still writing from abroad. Women’s solitary or “unescorted” travel, even in contemporary times, is considered less common in the Western world, with recurrent travel warnings constantly targeted at female travellers. Travelling women are always made aware of the limits of their body and its vulnerabilities. Mary Morris comments on “the fear of rape, for example, whether crossing the Sahara or just crossing a city street at night” (xvii). While a certain degree of danger always exists in travel for men and women alike and while it is inevitable that some of those risks are gender-specific, travel is frequently viewed as far more hazardous for women. Guide books, travel magazines and online advice columns targeted especially at female readers are cramped with words of concern and caution for women travellers. Often, the implicit message that women are too weak and vulnerable to travel is packaged neatly into “a cache of valuable advice” with shocking anecdotes and officious chapters such as “Dealing with Officials”, “Choosing Companions” or “If You Become a Victim” (Swan and Laufer vii). As these warnings are usually levelled at white, middle to upper class women who have the freedom and financing to travel, the question arises as to what is really at risk when women take to the road. It seems the usual dialogue between issues of mobility and issues of safety can be read more complexly as confusions between questions of mobility and morality. As Kristi Siegel explains, “among the various subtexts embedded in these travel warnings is the long-held fear of ‘women on the loose’” (4). According to Karen Lawrence, travel has always entailed a “risky and rewardingly excessive” terrain for women because of the historical link between wandering and promiscuity (240). Paul Hyland has even suggested that the nature of travel itself is “gloriously” promiscuous: “the shifting destination, arrival again and again, the unknown possessed, the quest for an illusory home” (211). This construction of female travel as a desire to wander connotes straying behaviours that are often cast in sexual terms. The identification of these traits in early criminological research, such as 19th century studies of cacogenic families, is often linked to travel in a broad sense. According to Nicolas Hahn’s study, Too Dumb to Know Better, contributors to the image of the “bad” woman frequently cite three traits as characteristic. “First, they have pictured her as irresolute and all too easily lead. Second, they have usually shown her to be promiscuous and a good deal more lascivious than her virtuous sister. Third, they have often emphasised the bad woman’s responsibility for not only her own sins, but those of her mate and descendents as well” (3). Like Eve, who wanders around the edge of the garden, the promiscuous woman has long been said to have a wandering disposition. Interestingly, however, both male and female travel writers have at different times and for dissimilar reasons assumed hermaphroditic identities while travelling. The female traveller, for example, may assume the figure of “the observer” or “the reporter with historical and political awareness”, while the male traveller may feminise his behaviours to confront inevitabilities of confinement and mortality (Fortunati, Monticelli and Ascari 11). Female travellers such as Alexandra David-Neel and Isabelle Eberhardt who ventured out of the home and cross-dressed for safety or success, deliberately and fully appropriated traditional roles of the male sex. Often, this attempt by female wanderers to fulfil their own intentions in cognito evaded their dismissal as wild and unruly women and asserted their power over those duped by their disguise. Those women who did travel openly into the world were often accused of flaunting the gendered norms of female decorum with their “so-called unnatural and inappropriate behaviour” (Siegel 3). The continued harnessing of this cultural taboo by popular media continues to shape contemporary patterns of female travel. In fact, as a result of perceived connections between wandering and danger, the narrative of the woman traveller often emerges as a self-conscious fiction where “the persona who emerges on the page is as much a character as a woman in a novel” (Bassnett 234). This process of self-fictionalising converts the travel writing into a graph of subliminal fears and desires. In Tracks, for example, which is Robyn Davidson’s account of her solitary journey by camel across the Australian desert, Davidson shares with her readers the single, unvarying warning she received from the locals while preparing for her expedition. That was, if she ventured into the desert alone without a guide or male accompaniment, she would be attacked and raped by an Aboriginal man. In her opening pages, Davidson recounts a conversation in the local pub when one of the “kinder regulars” warns her: “You ought to be more careful, girl, you know you’ve been nominated by some of these blokes as the next town rape case” (19). “I felt really frightened for the first time,” Davidson confesses (20). Perhaps no tale better depicts this gendered troubling than the fairytale of Little Red Riding Hood. In the earliest versions of the story, Little Red outwits the Wolf with her own cunning and escapes without harm. By the time the first printed version emerges, however, the story has dramatically changed. Little Red now falls for the guise of the Wolf, and tricked by her captor, is eaten without rescue or escape. Charles Perrault, who is credited with the original publication, explains the moral at the end of the tale, leaving no doubt to its intended meaning. “From this story one learns that children, especially young lasses, pretty, courteous and well-bred, do very wrong to listen to strangers, and it is not an unheard thing if the Wolf is thereby provided with his dinner” (77). Interestingly, in the Grimm Brothers’ version which emerges two centuries later an explicit warning now appears in the tale, in the shape of the mother’s instruction to “walk nicely and quietly, and not run off the path” (144). This new inclusion sanitises the tale and highlights the slippages between issues of mobility and morality. Where Little Red once set out with no instruction not to wander, she is now told plainly to stay on the path; not for her own safety but for implied matters of virtue. If Little Red strays while travelling alone she risks losing her virginity and, of course, her virtue (Siegel 55). Essentially, this is what is at stake when Little Red wanders; not that she will get lost in the woods and be unable to find her way, but that in straying from the path and purposefully disobeying her mother, she will no longer be “a dear little girl” (Grimm 144). In the Grimms’ version, Red Riding Hood herself critically reflects on her trespassing from the safe space of the village to the dangerous world of the forest and makes a concluding statement that demonstrates she has learnt her lesson. “As long as I live, I will never by myself leave the path, to run into the wood, when my mother has forbidden me to do so” (149). Red’s message to her female readers is representative of the social world’s message to its women travellers. “We are easily distracted and disobedient, we are not safe alone in the woods (travelling off the beaten path); we are fairly stupid; we get ourselves into trouble; and we need to be rescued by a man” (Siegel 56). As Siegel explains, even Angela Carter’s Red Riding Hood, who bursts out laughing when the Wolf says “all the better to eat you with” for “she knew she was nobody’s meat” (219), still shocks readers when she uses her virginity to take power over the voracious Wolf. In Carter’s world “children do not stay young for long,” and Little Red, who has her knife and is “afraid of nothing”, is certainly no exception (215). Yet in the end, when Red seduces the Wolf and falls asleep between his paws, there is still a sense this is a twist ending. As Siegel explains, “even given the background Carter provides in the story’s beginning, the scene startles. We knew the girl was strong, independent, and armed. However, the pattern of woman-alone-travelling-alone-helpless-alone-victim is so embedded in our consciousness we are caught off guard” (57). In Roald Dahl’s revolting rhyme, Little Red is also awarded agency, not through sexual prerogative, but through the enactment of traits often considered synonymous with male bravado: quick thinking, wit and cunning. After the wolf devours Grandmamma, Red pulls a pistol from her underpants and shoots him dead. “The small girl smiles. One eyelid flickers. She whips a pistol from her knickers. She aims it at the creature’s head and bang bang bang, she shoots him dead” (lines 48—51). In the weeks that follow Red’s triumph she even takes a trophy, substituting her red cloak for a “furry wolfskin coat” (line 57). While Dahl subverts female stereotypes through Red’s decisive action and immediacy, there is still a sense, perhaps heightened by the rhyming couplets, that we are not to take the shooting seriously. Instead, Red’s girrrl-power is an imagined celebration; it is something comical to be mused over, but its shock value lies in its impossibility; it is not at all believable. While the sexual overtones of the tale have become more explicit in contemporary film adaptations such as David Slade’s Hard Candy and Catherine Hardwicke’s Red Riding Hood, the question that arises is what is really at threat, or more specifically who is threatened, when women travel off the well-ordered path of duty. As this problematic continues to surface in discussions of the genre, other more nuanced readings have also distorted the purpose and practice of women’s travel. Some psychoanalytical theorists, for example, have adopted Freud’s notion of travel as an escape from the family, particularly the father figure. In his essay A Disturbance of Memory on the Acropolis, Freud explains how his own longing to travel was “a wish to escape from that pressure, like the force which drives so many adolescent children to run away from home” (237). “When one first catches sight of the sea,” Freud writes, “one feels oneself like a hero who has performed deeds of improbable greatness” (237). The inherent gender trouble with such a reading is the suggestion women only move in search of a quixotic male figure, “fleeing from their real or imaginary powerful fathers and searching for an idealised and imaginary ‘loving father’ instead” (Berger 55). This kind of thinking reduces the identities of modern women to fragile, unfinished selves, whose investment in travel is always linked to recovering or resisting a male self. Such readings neglect the unique history of women’s travel writing as they dismiss differences in the male and female practice and forget that “travel itself is a thoroughly gendered category” (Holland and Huggan 111). Freud’s experience of travel, for example, his description of feeling like a “hero” who has achieved “improbable greatness” is problematised by the female context, since the possibility arises that women may travel with different e/motions and, indeed, motives to their male counterparts. For example, often when a female character does leave home it is to escape an unhappy marriage, recover from a broken heart or search for new love. Elizabeth Gilbert’s best selling travelogue, Eat, Pray, Love (which spent 57 weeks at the number one spot of the New York Times), found its success on the premise of a once happily married woman who, reeling from a contentious divorce, takes off around the world “in search of everything” (1). Since its debut, the novel has been accused of being self-absorbed and sexist, and even branded by the New York Post as “narcissistic New Age reading, curated by Winfrey” (Callahan par 13). Perhaps most interesting for discussions of travel morality, however, is Bitch magazine’s recent article Eat, Pray, Spend, which suggests that the positioning of the memoir as “an Everywoman’s guide to whole, empowered living” typifies a new literature of privilege that excludes “all but the most fortunate among us from participating” (Sanders and Barnes-Brown par 7). Without seeking to limit the novel with separatist generalisations, the freedoms of Elizabeth Gilbert (a wealthy, white American novelist) to leave home and to write about her travels afterwards have not always been the freedoms of all women. As a result of this problematic, many contemporary women mark out alternative patterns of movement when travelling, often moving deliberately in a variety of directions and at varying paces, in an attempt to resist their placelessness in the travel genre and in the mappable world. As Heidi Slettedahl Macpherson, speaking of Housekeeping’s Ruthie and Sylvie, explains, “they do not travel ever westward in search of some frontier space, nor do they travel across great spaces. Rather, they circle, they drift, they wander” (199). As a result of this double displacement, women have to work twice as hard to be considered credible travellers, particularly since travel is traditionally a male discursive practice. In this tradition, the male is often constructed as the heroic explorer while the female is mapped as a place on his itinerary. She is a point of conquest, a land to be penetrated, a site to be mapped and plotted, but rarely a travelling equal. Annette Kolodny considers this metaphor of “land-as-woman” (67) in her seminal work, The Lay of the Land, in which she discusses “men’s impulse to alter, penetrate and conquer” unfamiliar space (87). Finally, it often emerges that even when female travel focuses specifically on an individual or collective female experience, it is still read in opposition to the long tradition of travelling men. In their introduction to Amazonian, Dea Birkett and Sara Wheeler maintain the primary difference between male and female travel writers is that “the male species” has not become extinct (vii). The pair, who have theorised widely on New Travel Writing, identify some of the myths and misconceptions of the female genre, often citing their own encounters with androcentrism in the industry. “We have found that even when people are confronted by a real, live woman travel writer, they still get us wrong. In the time allowed for questions after a lecture, we are regularly asked, ‘Was that before you sailed around the world or after?’ even though neither of us has ever done any such thing” (xvii). The obvious bias in such a comment is an archaic view of what qualifies as “good” travel and a preservation of the stereotypes surrounding women’s intentions in leaving home. As Birkett and Wheeler explain, “the inference here is that to qualify as travel writers women must achieve astonishing and record-breaking feats. Either that, or we’re trying to get our hands down some man’s trousers. One of us was once asked by the president of a distinguished geographical institution, ‘What made you go to Chile? Was it a guy?’” (xviii). In light of such comments, there remain traceable difficulties for contemporary female travel. As travel itself is inherently gendered, its practice has often been “defined by men according to the dictates of their experience” (Holland and Huggan 11). As a result, its discourse has traditionally reinforced male prerogatives to wander and female obligations to wait. Even the travel trade itself, an industry that often makes its profits out of preying on fear, continues to shape the way women move through the world. While the female traveller then may no longer preface her work with an explicit apology, there are still signs she is carrying some historical baggage. It is from this site of trouble that new patterns of female travel will continue to emerge, distinguishably and defiantly, towards a much more colourful vista of general misrule. References Bassnett, Susan. “Travel Writing and Gender.” The Cambridge Companion to Travel Writing, eds. Peter Hulme and Tim Youngs, Cambridge: Cambridge UP, 2002. 225-40. Berger, Arthur Asa. Deconstructing Travel: Cultural Perspectives on Tourism. Walnut Creek: AltaMira Press, 2004. Bird, Isabella. The Englishwoman in America. London: John Murray, 1856. Birkett, Dea, and Sara Wheeler, eds. Amazonian: The Penguin Book of New Women’s Travel Writing. London: Penguin, 1998. Callahan, Maureen. “Eat, Pray, Loathe: Latest Self-Help Bestseller Proves Faith is Blind.” New York Post 23 Dec. 2007. Carter, Angela. “The Company of Wolves.” Burning Your Boats: The Collected Short Stories. London: Vintage, 1995. 212-20. Dahl, Roald. Revolting Rhymes. London: Puffin Books, 1982. Davidson, Robyn. Tracks. London: Jonathan Cape, 1980. Fortunati, Vita, Rita Monticelli, and Maurizio Ascari, eds. Travel Writing and the Female Imaginary. Bologna: Patron Editore, 2001. Freud, Sigmund. “A Disturbance of Memory on the Acropolis.” The Standard Edition of the Complete Psychological Works of Sigmund Freud, vol. XXII. New Introductory Lectures on Psycho-Analysis and Other Works, 1936. 237-48. Gilbert, Elizabeth. Eat, Pray, Love: One Woman’s Search for Everything Across Italy, India and Indonesia. New Jersey: Penguin, 2007. Grimm, Jacob, and Wilhelm Grimm. “Little Red Riding Hood.” Grimms’ Fairy Tales, London: Jonathan Cape, 1962. 144-9. Hahn, Nicolas. “Too Dumb to Know Better: Cacogenic Family Studies and the Criminology of Women.” Criminology 18.1 (1980): 3-25. Hard Candy. Dir. David Slade. Lionsgate. 2005. Holland, Patrick, and Graham Huggan. Tourists with Typewriters: Critical Reflections on Contemporary Travel Writing. Ann Arbor: U of Michigan P, 2003. Howells, Elizabeth. “Apologizing for Authority: The Rhetoric of the Prefaces of Eliza Cook, Isabelle Bird, and Hannah More.” Professing Rhetoric: Selected Papers from the 2000 Rhetoric Society of America Conference, eds. F.J. Antczak, C. Coggins, and G.D. Klinger. London: Lawrence Erlbaum Associates, 2002. 131-7. Hyland, Paul. The Black Heart: A Voyage into Central Africa. New York: Paragon House, 1988. Kingsley, Mary. Travels in West Africa. Middlesex: The Echo Library, 2008. Kolodny, Annette. The Lay of the Land: Metaphor as Experience and History in American Life and Letters. USA: U of North Carolina P, 1975. Lawrence, Karen. Penelope Voyages: Women and Travel in the British Literary Tradition. Ithaca: Cornell UP, 1994. Morris, Mary. Maiden Voyages: Writings of Women Travellers. New York: Vintage Books, 1993. Perrault, Charles. Perrault’s Complete Fairytales. Trans. A.E. Johnson and others. London: Constable & Company, 1961. Red Riding Hood. Dir. Catherine Hardwicke. Warner Bros. 2011. Sanders, Joshunda, and Diana Barnes-Brown. “Eat, Pray, Spend: Priv-Lit and the New, Enlightened American Dream” Bitch Magazine 47 (2010). 10 May, 2011 < http://bitchmagazine.org/article/eat-pray-spend >. Siegel, Kristi. Ed. Gender, Genre, and Identity in Women’s Travel Writing. New York: Peter Lang, 2004. Slettedahl Macpherson, Heidi. “Women’s Travel Writing and the Politics of Location: Somewhere In-Between.” Gender, Genre, and Identity in Women’s Travel Writing, ed. Kristi Siegel. New York: Peter Lang, 2004. 194-207. Swan, Sheila, and Peter Laufer. Safety and Security for Women who Travel. 2nd ed. San Francisco: Travelers’ Tales, 2004. Woolf, Virginia. Women and Writing. London: The Women’s Press, 1979.

Efficient address translation mechanisms are gaining more and more attention as the virtual address range of the processors keeps expanding and the demand for machine virtualization increases with cloud and data center-based services. Traditional radix-tree based address translations can incur significant overheads in big data applications, particularly under virtualization, due to multi-level tree walks and nested translation. The overheads stem primarily from the unnecessary generality — ability to support several hundreds of thousands of virtual memory regions in the virtual address space — supported by current processors. We observe that in the common case, however, a process’s virtual address space contains only a few contiguously allocated sections, which can be efficiently translated using a shallow tree with two levels. We propose such a compact structure, called 2-Level Page Table(2-LPT), which serves as a key building block for address translation in virtualized environment. A key advantage of 2-LPT is that it maintains two levels of page tables irrespective of the size of the virtual address space. Translating a virtual address using 2-LPT is fast. A walk on a 2-LPT requires up to two memory accesses. In practice, however, the root level table is well cached in the Page Walk Caches, thus, single memory access is sufficient. Under native execution, 2-LPT reduces the page walk latency by up to 20.9% (9.38% on average) and improves performance by up to 10.1% (1.66% on average) over the conventional four-level radix tree page tables, on a set of memory-intensive applications. 2-LPT is more beneficial under virtualization. A naive extension of 2-LPT reduces the cost of nested page walk from 24 to 8 memory accesses. To achieve further reduction, we propose two optimizations: (i) Enhanced Partial Shadow Paging (ePSP) which employs a limited form of shadow paging for the root-level of 2-LPT, and (ii) Host PTE Mirroring (HPM) which allows accessing the host page table entry without performing host page table walk. These optimizations reduce the number of memory accesses to just one, on average, while avoiding slow VM exits. 2-LPT speeds up applications by 5.6%-50.9% (24.6%, on average) over the baseline nested page walks. Compared to the best performing state-of-the-art proposal, 2-LPT achieves an average reduction of 41.5% and 15.7% in page walk latency and execution cycles