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From: Mike Marshall <>
To: Matthew Wilcox <>
Cc:, Christoph Hellwig <>,,
	linux-fsdevel <>
Subject: Re: [PATCH] orangefs: complete Christoph's "remember count" reversion.
Date: Sat, 4 Apr 2020 16:57:24 -0400	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

Matthew>  So yes, I think within the next year, you should be
Matthew>  able to tell the page cache to allocate 4MB pages.

I can't find the ascii thumbs up emoji :-) ...


On Sat, Apr 4, 2020 at 1:43 PM Matthew Wilcox <> wrote:
> On Sat, Apr 04, 2020 at 12:28:26PM -0400, wrote:
> > As an aside, the page cache has been a blessing and a curse
> > for us. Since we started using it, small IO has improved
> > incredibly, but our max speed hits a plateau before it otherwise
> > would have. I think because of all the page size copies we have
> > to do to fill our 4 meg native buffers. I try to read about all
> > the new work going into the page cache in lwn, and make some
> > sense of the new code :-). One thing I remember is when
> > Christoph Lameter said "the page cache does not scale", but
> > I know the new work is focused on that. If anyone has any
> > thoughts about how we could make improvments on filling our
> > native buffers from the page cache (larger page sizes?),
> > feel free to offer any help...
> Umm, 4MB native buffers are ... really big ;-)  I wasn't planning on
> going past PMD_SIZE (ie 2MB on x86) for the readahead large pages,
> but if a filesystem wants that, then I should change that plan.
> What I was planning for, but don't quite have an implementation nailed
> down for yet, is allowing filesystems to grow the readahead beyond that
> wanted by the generic code.  Filesystems which implement compression
> frequently want blocks in the 256kB size range.  It seems like OrangeFS
> would fit with that scheme, as long as I don't put a limit on what the
> filesystem asks for.
> So yes, I think within the next year, you should be able to tell the
> page cache to allocate 4MB pages.  You will still need a fallback path
> for when memory is too fragmented to allocate new pages, but if you're
> using 4MB pages, then hopefully we'll be able to reclaim a clean 4MB
> pages from elsewhere in the page cache and supply you with a new one.

  reply	other threads:[~2020-04-04 20:57 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-03-26 17:07 orangefs fixes Christoph Hellwig
2020-03-26 17:07 ` [PATCH 1/2] Revert "orangefs: remember count when reading." Christoph Hellwig
2020-03-31 13:55   ` Mike Marshall
2020-04-04 16:28   ` [PATCH] orangefs: complete Christoph's "remember count" reversion hubcap
2020-04-04 17:43     ` Matthew Wilcox
2020-04-04 20:57       ` Mike Marshall [this message]
2020-03-26 17:07 ` [PATCH 2/2] orangefs: don't mess with I_DIRTY_TIMES in orangefs_flush Christoph Hellwig

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