Messages in this thread | | | Date | Mon, 28 Jul 2008 17:17:28 -0700 | From | Andrew Morton <> | Subject | Re: PERF: performance tests with the split LRU VM in -mm |
| |
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 mlock-downgrade-mmap-sem-while-populating-mlocked-regions.patch mmap-handle-mlocked-pages-during-map-remap-unmap.patch
that patch fixes?
| |