From: Trond Myklebust <trond.myklebust@fys.uio.no>
To: Jeff Layton <jlayton@redhat.com>
Cc: "J. Bruce Fields" <bfields@fieldses.org>, linux-nfs@vger.kernel.org
Subject: Re: [PATCH] knfsd: allocate readahead cache in individual chunks
Date: Thu, 14 Aug 2008 15:11:26 -0400 [thread overview]
Message-ID: <1218741086.7328.24.camel@localhost> (raw)
In-Reply-To: <20080814145227.15efe087-xSBYVWDuneFaJnirhKH9O4GKTjYczspe@public.gmane.org>
On Thu, 2008-08-14 at 14:52 -0400, Jeff Layton wrote:
> 1) do what I did here (individual kmalloc for each raparm)
>
> 2) do an allocation of an raparms array for each hash bucket, but when
> we get to larger thread counts, these will still require multi-page
> allocations:
>
> 8192 threads * 2 / 16 buckets * 72 bytes = 73728 byte allocation
>
> 3) declare a separate slabcache for this and allocate each raparm
> individually from that
>
> ...#3 might be reasonable, but we could end up wasting even more memory
> that way when we only have a few threads. Tough call...
How about
4) Set an upper cap on the size of the raparm array
Readahead is only useful in moderation. You don't want to reach a
situation where the various threads' readahead activities start causing
thrashing...
Cheers
Trond
next prev parent reply other threads:[~2008-08-14 19:11 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-08-14 2:03 [PATCH] knfsd: allocate readahead cache in individual chunks Jeff Layton
2008-08-14 18:06 ` J. Bruce Fields
2008-08-14 18:52 ` Jeff Layton
[not found] ` <20080814145227.15efe087-xSBYVWDuneFaJnirhKH9O4GKTjYczspe@public.gmane.org>
2008-08-14 19:11 ` Trond Myklebust [this message]
2008-08-14 19:14 ` Jeff Layton
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