On Wed, Dec 16, 2020 at 03:54:29PM +0100, Vasilis Liaskovitis wrote:
> Avoid computing the number of bytes in shmall, by only
> computing the number of Kbytes. This improves some
> overflows, e.g.
>
> $ echo "4503599627370496" > /proc/sys/kernel/shmall
> $ ipcs -l | grep 'max total shared memory'
> Before:
> max total shared memory (kbytes) = 18014398509481980
> After:
> max total shared memory (kbytes) = 18014398509481984
>
> $ echo "99993599627370500" > /proc/sys/kernel/shmall
> 99993599627370500
> $ ipcs -l | grep 'max total shared memory'
> Before:
> max total shared memory (kbytes) = 18014398509481980
> After:
> max total shared memory (kbytes) = 399974398509482000
>
> Signed-off-by: Vasilis Liaskovitis <vliaskovitis@xxxxxxxx>
> ---
> sys-utils/ipcs.c | 10 +++-------
> 1 file changed, 3 insertions(+), 7 deletions(-)
>
> diff --git a/sys-utils/ipcs.c b/sys-utils/ipcs.c
> index fc6fba4a6..544a3adcc 100644
> --- a/sys-utils/ipcs.c
> +++ b/sys-utils/ipcs.c
> @@ -216,13 +216,9 @@ static void do_shm (char format, int unit)
> ipc_print_size(unit == IPC_UNIT_DEFAULT ? IPC_UNIT_KB :
> unit,
> _("max seg size"), lim.shmmax, "\n", 0);
>
> - tmp = (uint64_t) lim.shmall * pgsz;
> - /* overflow handling, at least we don't print
> ridiculous small values */
> - if (lim.shmall != 0 && tmp / lim.shmall != pgsz) {
> - tmp = UINT64_MAX - (UINT64_MAX % pgsz);
> - }
> - ipc_print_size(unit == IPC_UNIT_DEFAULT ? IPC_UNIT_KB :
> unit,
> - _("max total shared memory"), tmp, "\n",
> 0);
> + ipc_print_size(IPC_UNIT_DEFAULT,
> + _("max total shared memory (kbytes)"),
> (pgsz / 1024) *
> + (uint64_t) lim.shmall, "\n", 0);
It means that --bytes and --human command line options will be
ignored for shmall ... it would be probably better to use
if (unit == IPC_UNIT_KB || units == IPC_UNIT_DEFAULT)
ipc_print_size(IPC_UNIT_KB, ("max total shared memory"), lim.shmall, "\n", 0);
else {
tmp = (uint64_t) lim.shmall * pgsz;
/* overflow handling, at least we don't print ridiculous small values */
if (lim.shmall != 0 && tmp / lim.shmall != pgsz)
tmp = UINT64_MAX - (UINT64_MAX % pgsz);
ipc_print_size(unit, _("max total shared memory"), tmp, "\n", 0);
}
Right? If yes, update the patch, please.
Karel
--
Karel Zak <kzak@xxxxxxxxxx>
http://karelzak.blogspot.com
