Messages in this thread | | | Subject | Re: PERF: performance tests with the split LRU VM in -mm | From | Lee Schermerhorn <> | Date | Mon, 28 Jul 2008 20:46:46 -0400 |
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On Mon, 2008-07-28 at 17:17 -0700, Andrew Morton wrote: > On Mon, 28 Jul 2008 20:03:11 -0400 > Rik van Riel <riel@redhat.com> wrote: > > > On Mon, 28 Jul 2008 19:57:13 -0400 > > Rik van Riel <riel@redhat.com> wrote: > > > On Mon, 28 Jul 2008 16:41:24 -0700 > > > Andrew Morton <akpm@linux-foundation.org> wrote: > > > > > > > > Andrew, what is your preference between: > > > > > http://lkml.org/lkml/2008/7/15/465 > > > > > and > > > > > http://marc.info/?l=linux-mm&m=121683855132630&w=2 > > > > > > > > > > > > > Boy. They both seem rather hacky special-cases. But that doesn't mean > > > > that they're undesirable hacky special-cases. I guess the second one > > > > looks a bit more "algorithmic" and a bit less hacky-special-case. But > > > > it all depends on testing.. > > > > > > I prefer the second one, since it removes the + 1 magic (at least, > > > for the higher priorities), instead of adding new magic like the > > > other patch does. > > > > Btw, didn't you add that "+ 1" originally early on in the 2.6 VM? > > You mean this? > > /* > * Add one to nr_to_scan just to make sure that the kernel > * will slowly sift through the active list. > */ > zone->nr_scan_active += > (zone_page_state(zone, NR_ACTIVE) >> priority) + 1; > > > > Do you remember its purpose? > > erm, not specifically, but I tended to lavishly describe changes like > this in the changelogging. > > > Does it still make sense to have that "+ 1" in the split LRU VM? > > > > Could we get away with just removing it unconditionally? > > We should do the necessary git dumpster-diving before tossing out > hard-won changes. Otherwise we might need to spend a year > re-discovering and re-fixing already-discovered-and-fixed things. > > That code has been there in one way or another for some time. > > In June 2004, 385c0449 did this: > > /* > - * Try to keep the active list 2/3 of the size of the cache. And > - * make sure that refill_inactive is given a decent number of pages. > - * > - * The "scan_active + 1" here is important. With pagecache-intensive > - * workloads the inactive list is huge, and `ratio' evaluates to zero > - * all the time. Which pins the active list memory. So we add one to > - * `scan_active' just to make sure that the kernel will slowly sift > - * through the active list. > + * Add one to `nr_to_scan' just to make sure that the kernel will > + * slowly sift through the active list. > */ > - if (zone->nr_active >= 4*(zone->nr_inactive*2 + 1)) { > - /* Don't scan more than 4 times the inactive list scan size */ > - scan_active = 4*scan_inactive; > > (there was some regrettable information loss there). > > Is the scenario which that fix addresses no longer possible? > > > On a different topic, I am staring in frustration at > introduce-__get_user_pages.patch, which says: > > New munlock processing need to GUP_FLAGS_IGNORE_VMA_PERMISSIONS. > because current get_user_pages() can't grab PROT_NONE pages theresore > it cause PROT_NONE pages can't munlock. > > could someone please work out for me which of these patches: > > vmscan-move-isolate_lru_page-to-vmscanc.patch > vmscan-use-an-indexed-array-for-lru-variables.patch > swap-use-an-array-for-the-lru-pagevecs.patch > vmscan-free-swap-space-on-swap-in-activation.patch > define-page_file_cache-function.patch > vmscan-split-lru-lists-into-anon-file-sets.patch > vmscan-second-chance-replacement-for-anonymous-pages.patch > vmscan-fix-pagecache-reclaim-referenced-bit-check.patch > vmscan-add-newly-swapped-in-pages-to-the-inactive-list.patch > more-aggressively-use-lumpy-reclaim.patch > pageflag-helpers-for-configed-out-flags.patch > unevictable-lru-infrastructure.patch > unevictable-lru-page-statistics.patch > ramfs-and-ram-disk-pages-are-unevictable.patch > shm_locked-pages-are-unevictable.patch > mlock-mlocked-pages-are-unevictable.patch
Andrew:
Kosaki-san's patch to introduce __get_user_pages() is a patch to the above unevictable, mlocked pages. He enhanced get_user_pages() so that we could fault in PROT_NONE pages for munlocking, to replace the page table walker [subsequent patches in that series]. He replaced the page table walker to avoid the "sleeping while atomic" for 32-bit/HIGHPTE configs.
Lee
> mlock-downgrade-mmap-sem-while-populating-mlocked-regions.patch > mmap-handle-mlocked-pages-during-map-remap-unmap.patch > > that patch fixes? > > -- > To unsubscribe, send a message with 'unsubscribe linux-mm' in > the body to majordomo@kvack.org. For more info on Linux MM, > see: http://www.linux-mm.org/ . > Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
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