linux-kernel - Re: Problem with /proc/sys/vm/lowmem_reserve

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Message-ID: <x49wsp272se.fsf@segfault.boston.devel.redhat.com>
Date:	Mon, 18 Feb 2008 09:33:05 -0500
From:	Jeff Moyer <jmoyer@...hat.com>
To:	Larry Woodman <lwoodman@...hat.com>
Cc:	linux-kernel@...r.kernel.org, riel@...hat.com
Subject: Re: Problem with /proc/sys/vm/lowmem_reserve_ratio ???

Larry Woodman <lwoodman@...hat.com> writes:

> balance_pgdat() calls zone_watermark_ok() three times, the first call
> passes a zero(0) in as the 4th argument.  This 4th argument is the
> classzone_idx which is used as the index into the
> zone->lowmem_reserve[] array.  Since setup_per_zone_lowmem_reserve()
> always sets the zone->lowmem_reserve[0] = 0(because there is nothing
> below the DMA zone), zone_watermark_ok() will not consider the
> lowmem_reserve pages when zero is passed as the 4th arg.  Shouldnt this
> 4th argument be either "i" or "nr_zones - 1" ???

That certainly looks like the intent of this code.  I'd say patch 1,
passing i in as the 4th arg.  Rik, what do you think?

Cheers,

Jeff

>
> -------------------------------------------------------------------------
> --- linux-2.6.24.noarch/mm/vmscan.c.orig        2008-02-13
> 11:14:55.000000000 -0500
> +++ linux-2.6.24.noarch/mm/vmscan.c     2008-02-13 11:15:02.000000000
> -0500
> @@ -1375,7 +1375,7 @@ loop_again:
>                                continue;
>
>                        if (!zone_watermark_ok(zone, order, zone->pages_high,
>
> -                                              0, 0)) {
> +                                              i, 0)) {
>                                end_zone = i;
>                                break;
> -------------------------------------------------------------------------
> --- linux-2.6.24.noarch/mm/vmscan.c.orig        2008-02-13
> 11:14:55.000000000 -0500
> +++ linux-2.6.24.noarch/mm/vmscan.c     2008-02-13 11:16:35.000000000
> -0500
> @@ -1375,7 +1375,7 @@ loop_again:
>                                continue;
>
>                        if (!zone_watermark_ok(zone, order, zone->pages_high,
>
> -                                              0, 0)) {
> +                                              nr_zones - 1, 0)) {
>                                end_zone = i;
>                                break;
>                        }
> -------------------------------------------------------------------------
--
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