From: Matthew Wilcox <willy@infradead.org>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
linux-mm@kvack.org, linux-fsdevel@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [GIT PULL] Two folio fixes for 5.18
Date: Tue, 10 May 2022 23:30:02 +0100 [thread overview]
Message-ID: <YnrnaoCVjAZfqNvW@casper.infradead.org> (raw)
In-Reply-To: <20220510151809.f06c7580af34221c16003264@linux-foundation.org>
On Tue, May 10, 2022 at 03:18:09PM -0700, Andrew Morton wrote:
> On Fri, 6 May 2022 00:43:18 +0100 Matthew Wilcox <willy@infradead.org> wrote:
>
> > - Fix readahead creating single-page folios instead of the intended
> > large folios when doing reads that are not a power of two in size.
>
> I worry about the idea of using hugepages in readahead. We're
> increasing the load on the hugepage allocator, which is already
> groaning under the load.
Well, hang on. We're not using the hugepage allocator, we're using
the page allocator. We're also using variable order pages, not
necessarily PMD_ORDER. I was under the impression that we were
using GFP_TRANSHUGE_LIGHT, but I now don't see that. So that might
be something that needs to be changed.
> The obvious risk is that handing out hugepages to a low-value consumer
> (copying around pagecache which is only ever accessed via the direct
> map) will deny their availability to high-value consumers (that
> compute-intensive task against a large dataset).
>
> Has testing and instrumentation been used to demonstrate that this is
> not actually going to be a problem, or are we at risk of getting
> unhappy reports?
It's hard to demonstrate that it's definitely not going to cause a
problem. But I actually believe it will help; by keeping page cache
memory in larger chunks, we make it easier to defrag memory and create
PMD-order pages when they're needed.
next prev parent reply other threads:[~2022-05-10 22:30 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-05-05 23:43 [GIT PULL] Two folio fixes for 5.18 Matthew Wilcox
2022-05-06 0:02 ` pr-tracker-bot
2022-05-10 22:18 ` Andrew Morton
2022-05-10 22:30 ` Matthew Wilcox [this message]
2022-05-10 22:45 ` Andrew Morton
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