linux-kernel - Re: [PATCH 0/1] ipc/util.{c,h}: Use binary search for max

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Date:   Sun, 25 Apr 2021 11:07:29 -0700
From:   Davidlohr Bueso <dave@...olabs.net>
To:     Manfred Spraul <manfred@...orfullife.com>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Andrew Morton <akpm@...ux-foundation.org>, 1vier1@....de
Subject: Re: [PATCH 0/1] ipc/util.{c,h}: Use binary search for max_idx

On Sun, 25 Apr 2021, Manfred Spraul wrote:

>2nd version of the patch:
>@Andrew: Could you add the patch to your mm tree, as candidate for
>linux-next?
>
>Note:
>I have tried to remove the ids->max_idx cache entirely. Unfortunately,
>this causes a significant slow-down of semstat(,,IPC_STAT):
>   * no object allocated, no ipcmni_extended: +50%
>   * no object allocated, with ipcmni_extended: +80%
>   * 30 objects allocated, with large gaps, no ipcmni_extended:
>           +350%
>Thus I haven't removed ids->max_id.

Right, IPC_STAT is the main usecase for max_id. But I'm not sure why
you were looking to remove it in the first place - or was it just to
avoid this patch altogether?

Thanks,
Davidlohr