From: Olivier MATZ <olivier.matz@6wind.com>
To: Stephen Hemminger <stephen@networkplumber.org>, dev@dpdk.org
Subject: Re: [dpdk-dev] [PATCH] mempool: avoid memory waste with large pagesize
Date: Wed, 9 Mar 2016 18:49:45 +0100 [thread overview]
Message-ID: <56E06239.3060008@6wind.com> (raw)
In-Reply-To: <1457490571-24429-1-git-send-email-stephen@networkplumber.org>
On 03/09/2016 03:29 AM, Stephen Hemminger wrote:
> If page size is large (like 64K on ARM) and object size is small
> then don't waste lots of memory by rounding up to page size.
> Instead, round up so that 1 or more objects all fit in a page.
>
> This preserves the requirement that an object must not a page
> or virt2phys would break, and makes sure 62K is not wasted per mbuf.
You should specify that it only affects runs with "--no-huge".
> --- a/lib/librte_mempool/rte_mempool.c
> +++ b/lib/librte_mempool/rte_mempool.c
> @@ -300,18 +300,24 @@ rte_mempool_calc_obj_size(uint32_t elt_size, uint32_t flags,
> if (! rte_eal_has_hugepages()) {
> /*
> * compute trailer size so that pool elements fit exactly in
> - * a standard page
> + * a standard page. If elements are smaller than a page
> + * then allow multiple elements per page
> */
> - int page_size = getpagesize();
> - int new_size = page_size - sz->header_size - sz->elt_size;
> - if (new_size < 0 || (unsigned int)new_size < sz->trailer_size) {
> + unsigned page_size = getpagesize();
> + uint32_t orig_size, new_size;
> +
> + orig_size = sz->header_size + sz->elt_size;
> + new_size = rte_align32pow2(orig_size);
> + if (new_size > page_size) {
> printf("When hugepages are disabled, pool objects "
> "can't exceed PAGE_SIZE: %d + %d + %d > %d\n",
> sz->header_size, sz->elt_size, sz->trailer_size,
> page_size);
> return 0;
> }
> - sz->trailer_size = new_size;
> +
> + sz->trailer_size = (new_size - orig_size)
> + / (page_size / new_size);
> }
Looks it does not work, did I miss something?
Examples:
# start with --no-huge
mp = rte_mempool_create("test", 128,
35, 0, 0, NULL, NULL, NULL, NULL, SOCKET_ID_ANY, 0);
rte_mempool_dump(stdout, mp);
shows:
header_size=64
elt_size=40
trailer_size=0
total_obj_size=104 <<<<< should be 128?
# start with --no-huge
mp = rte_mempool_create("test", 128,
191, 0, 0, NULL, NULL, NULL, NULL, SOCKET_ID_ANY,
MEMPOOL_F_NO_CACHE_ALIGN);
rte_mempool_dump(stdout, mp);
shows:
header_size=8
elt_size=192
trailer_size=3
total_obj_size=203 <<<<< should be 256?
The RFC I've just submitted also aims to fix this issue
(but differently).
Regards,
Olivier
prev parent reply other threads:[~2016-03-09 17:49 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-03-09 2:29 Stephen Hemminger
2016-03-09 17:49 ` Olivier MATZ [this message]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=56E06239.3060008@6wind.com \
--to=olivier.matz@6wind.com \
--cc=dev@dpdk.org \
--cc=stephen@networkplumber.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).