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Date: Mon, 4 Jun 2007 16:28:55 +0200
From: Eric Dumazet <dada1@cosmosbay.com>
To: Davide Libenzi <davidel@xmailserver.org>
Cc: Andrew Morton <akpm@linux-foundation.org>, Ingo Molnar <mingo@elte.hu>,
       Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
       Linus Torvalds <torvalds@linux-foundation.org>,
       Ulrich Drepper <drepper@redhat.com>
Subject: Re: [patch 1/2] ufd v1 - unsequential O(1) fdmap core
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On Mon, 4 Jun 2007 06:35:16 -0700 (PDT)
Davide Libenzi <davidel@xmailserver.org> wrote:

> On Mon, 4 Jun 2007, Eric Dumazet wrote:
> 
> > You add conditional branches on very hot spots.
> 
> Keep BS for the ones you argue usually, and that are not able to reply.
> You *still* two bitmaps, because allocation spaces are far apart. So the 
> "if" will still be there.

I actually read your patches and spent time to see the pros and cons.

If you dont need reviewers, please dont post your patches on lkml.

If I am not mistaken, you added a test in fget()/fget_light(), which is a known hot point for said huge processes.

fget() dont need to access the bitmap at all. Using fd_slots means less (50%) file pointers per cache line.

On my machines, there is a ratio of 100/1 in cpu time for fget(),fget_light() against get_unused_fd().