Messages in this thread | | | Date | Thu, 15 Mar 2007 15:06:01 -0700 | From | Andrew Morton <> | Subject | Re: [PATCH] mm/filemap.c: unconditionally call mark_page_accessed |
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On Thu, 15 Mar 2007 22:49:23 +0100 Andrea Arcangeli <andrea@suse.de> wrote:
> On Thu, Mar 15, 2007 at 11:07:35AM -0800, Andrew Morton wrote: > > > On Thu, 15 Mar 2007 01:22:45 -0400 (EDT) Ashif Harji <asharji@cs.uwaterloo.ca> wrote: > > > I still think the simple fix of removing the > > > condition is the best approach, but I'm certainly open to alternatives. > > > > Yes, the problem of falsely activating pages when the file is read in small > > hunks is worse than the problem which your patch fixes. > > Really? I would have expected all performance sensitive apps to read > in >=PAGE_SIZE chunks. And if they don't because they split their > dataset in blocks (like some database), it may not be so wrong to > activate those pages that have two "hot" blocks more aggressively than > those pages with a single hot block.
But the problem which is being fixed here is really obscure: an application repeatedly reading the first page and only the first page of a file, always via the same fd.
I'd expect that the sub-page-size read scenarion happens heaps more often than that, especially when dealing with larger PAGE_SIZEs.
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