linux-kernel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Nick Piggin <nickpiggin@yahoo.com.au>
To: Christoph Lameter <clameter@sgi.com>
Cc: "Luck, Tony" <tony.luck@intel.com>, Robin Holt <holt@sgi.com>,
	Adam Litke <agl@us.ibm.com>,
	linux-ia64@vger.kernel.org, torvalds@osdl.org,
	linux-mm@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: Increase page fault rate by prezeroing V1 [2/3]: zeroing and scrubd
Date: Sat, 01 Jan 2005 13:22:04 +1100	[thread overview]
Message-ID: <41D6094C.3040908@yahoo.com.au> (raw)
In-Reply-To: <Pine.LNX.4.58.0412211156090.1313@schroedinger.engr.sgi.com>

Christoph Lameter wrote:
> o Add page zeroing
> o Add scrub daemon
> o Add ability to view amount of zeroed information in /proc/meminfo
> 

I quite like how you're handling the page zeroing now. It seems
less intrusive and cleaner in its interface to the page allocator
now.

I think this is pretty close to what I'd be happy with if we decide
to go with zeroing.

Just one small comment - there is a patch in the -mm tree that may
be of use to you; mm-keep-count-of-free-areas.patch is used later
by kswapd to handle and account higher order free areas properly.
You may be able to use it to better implement triggers/watermarks
for the scrub daemon.

Also...

> +
> +/*
> + * zero_highest_order_page takes a page off the freelist
> + * and then hands it off to block zeroing agents.
> + * The cleared pages are added to the back of
> + * the freelist where the page allocator may pick them up.
> + */
> +int zero_highest_order_page(struct zone *z)
> +{
> +	int order;
> +
> +	for(order = MAX_ORDER-1; order >= sysctl_scrub_stop; order--) {
> +		struct free_area *area = z->free_area[NOT_ZEROED] + order;
> +		if (!list_empty(&area->free_list)) {
> +			struct page *page = scrubd_rmpage(z, area, order);
> +			struct list_head *l;
> +
> +			if (!page)
> +				continue;
> +
> +			page->index = order;
> +
> +			list_for_each(l, &zero_drivers) {
> +				struct zero_driver *driver = list_entry(l, struct zero_driver, list);
> +				unsigned long size = PAGE_SIZE << order;
> +
> +				if (driver->start(page_address(page), size) == 0) {
> +
> +					unsigned ticks = (size*HZ)/driver->rate;
> +					if (ticks) {
> +						/* Wait the minimum time of the transfer */
> +						current->state = TASK_INTERRUPTIBLE;
> +						schedule_timeout(ticks);
> +					}
> +					/* Then keep on checking until transfer is complete */
> +					while (!driver->check())
> +						schedule();
> +					goto out;
> +				}

Would you be better off to just have a driver->zero_me(...) call, with this
logic pushed into those like your BTE which need it? I'm thinking this would
help flexibility if you had say a BTE-thingy that did an interrupt on
completion, or if it was done synchronously by the CPU with cache bypassing
stores.

Also, would there be any use in passing a batch of pages to the zeroing driver?
That may improve performance on some implementations, but could also cut down
the inefficiency in your timeout mechanism due to timer quantization (I guess
probably not much if you are only zeroing quite large areas).

BTW, that while loop is basically a busy-wait. Not a critical problem, but you
may want to renice scrubd to the lowest scheduling priority to be a bit nicer?
(I think you'd want to do that anyway). And put a cpu_relax() call in there?

Just some suggestions.

Nick

  reply	other threads:[~2005-01-01  2:22 UTC|newest]

Thread overview: 87+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <B8E391BBE9FE384DAA4C5C003888BE6F02900FBD@scsmsx401.amr.corp.intel.com>
     [not found] ` <41C20E3E.3070209@yahoo.com.au>
2004-12-21 19:55   ` Increase page fault rate by prezeroing V1 [0/3]: Overview Christoph Lameter
2004-12-21 19:56     ` Increase page fault rate by prezeroing V1 [1/3]: Introduce __GFP_ZERO Christoph Lameter
2004-12-21 19:57     ` Increase page fault rate by prezeroing V1 [2/3]: zeroing and scrubd Christoph Lameter
2005-01-01  2:22       ` Nick Piggin [this message]
2005-01-01  2:55         ` pmarques
2004-12-21 19:57     ` Increase page fault rate by prezeroing V1 [3/3]: Altix SN2 BTE Zeroing Christoph Lameter
2004-12-22 12:46       ` Robin Holt
2004-12-22 19:56         ` Christoph Lameter
2004-12-23 19:29     ` Prezeroing V2 [0/3]: Why and When it works Christoph Lameter
2004-12-23 19:33       ` Prezeroing V2 [1/4]: __GFP_ZERO / clear_page() removal Christoph Lameter
2004-12-23 19:33         ` Prezeroing V2 [2/4]: add second parameter to clear_page() for all arches Christoph Lameter
2004-12-24  8:33           ` Pavel Machek
2004-12-24 16:18             ` Christoph Lameter
2004-12-24 16:27               ` Pavel Machek
2004-12-24 17:02                 ` David S. Miller
2004-12-24 17:05           ` David S. Miller
2004-12-27 22:48             ` David S. Miller
2005-01-03 17:52             ` Christoph Lameter
2005-01-01 10:24           ` Geert Uytterhoeven
2005-01-04 23:12             ` Prezeroing V3 [0/4]: Discussion and i386 performance tests Christoph Lameter
2005-01-04 23:13               ` Prezeroing V3 [1/4]: Allow request for zeroed memory Christoph Lameter
2005-01-04 23:45                 ` Dave Hansen
2005-01-05  1:16                   ` Christoph Lameter
2005-01-05  1:26                     ` Linus Torvalds
2005-01-05 23:11                       ` Christoph Lameter
2005-01-05  0:34                 ` Linus Torvalds
2005-01-05  0:47                   ` Andrew Morton
2005-01-05  1:15                     ` Christoph Lameter
2005-01-08 21:12                 ` Hugh Dickins
2005-01-08 21:56                   ` David S. Miller
2005-01-21 20:09                     ` alloc_zeroed_user_highpage to fix the clear_user_highpage issue Christoph Lameter
2005-02-09  9:58                       ` [Patch] Fix oops in alloc_zeroed_user_highpage() when page is NULL Michael Ellerman
2005-02-10  0:38                         ` Christoph Lameter
2005-01-21 20:12                     ` Extend clear_page by an order parameter Christoph Lameter
2005-01-21 22:29                       ` Paul Mackerras
2005-01-21 23:48                         ` Christoph Lameter
2005-01-22  0:35                           ` Paul Mackerras
2005-01-22  0:43                             ` Andrew Morton
2005-01-22  1:08                               ` Paul Mackerras
2005-01-22  1:20                               ` Roman Zippel
2005-01-22  1:25                               ` Paul Mackerras
2005-01-22  1:54                                 ` Christoph Lameter
2005-01-22  2:53                                   ` Paul Mackerras
2005-01-23  7:45                       ` Andrew Morton
2005-01-24 16:37                         ` Christoph Lameter
2005-01-24 20:23                           ` David S. Miller
2005-01-24 20:33                             ` Christoph Lameter
2005-01-21 20:15                     ` A scrub daemon (prezeroing) Christoph Lameter
2005-01-10 17:16                   ` Prezeroing V3 [1/4]: Allow request for zeroed memory Christoph Lameter
2005-01-10 18:13                     ` Linus Torvalds
2005-01-10 20:17                       ` Christoph Lameter
2005-01-10 23:53                       ` Prezeroing V4 [0/4]: Overview Christoph Lameter
2005-01-10 23:54                         ` Prezeroing V4 [1/4]: Arch specific page zeroing during page fault Christoph Lameter
2005-01-11  0:41                           ` Chris Wright
2005-01-11  0:46                             ` Christoph Lameter
2005-01-11  0:49                               ` Chris Wright
2005-01-10 23:55                         ` Prezeroing V4 [2/4]: Zeroing implementation Christoph Lameter
2005-01-10 23:55                         ` Prezeroing V4 [3/4]: Altix SN2 BTE zero driver Christoph Lameter
2005-01-10 23:56                         ` Prezeroing V4 [4/4]: Extend clear_page to take an order parameter Christoph Lameter
2005-01-04 23:14               ` Prezeroing V3 [2/4]: Extension of " Christoph Lameter
2005-01-05 23:25                 ` Christoph Lameter
2005-01-06 13:52                   ` Andi Kleen
2005-01-06 17:47                     ` Christoph Lameter
2005-01-04 23:15               ` Prezeroing V3 [3/4]: Page zeroing through kscrubd Christoph Lameter
2005-01-04 23:16               ` Prezeroing V3 [4/4]: Driver for hardware zeroing on Altix Christoph Lameter
2005-01-05  2:16                 ` Andi Kleen
2005-01-05 16:24                   ` Christoph Lameter
2004-12-23 19:34         ` Prezeroing V2 [3/4]: Add support for ZEROED and NOT_ZEROED free maps Christoph Lameter
2004-12-23 19:35         ` Prezeroing V2 [4/4]: Hardware Zeroing through SGI BTE Christoph Lameter
2004-12-23 20:08         ` Prezeroing V2 [1/4]: __GFP_ZERO / clear_page() removal Brian Gerst
2004-12-24 16:24           ` Christoph Lameter
2004-12-23 19:49       ` Prezeroing V2 [0/3]: Why and When it works Arjan van de Ven
2004-12-23 20:57       ` Matt Mackall
2004-12-23 21:01       ` Paul Mackerras
2004-12-23 21:11       ` Paul Mackerras
2004-12-23 21:37         ` Andrew Morton
2004-12-23 23:00           ` Paul Mackerras
2004-12-23 21:48         ` Linus Torvalds
2004-12-23 22:34           ` Zwane Mwaikambo
2004-12-24  9:14           ` Arjan van de Ven
2004-12-24 18:21             ` Linus Torvalds
2004-12-24 18:57               ` Arjan van de Ven
2004-12-27 22:50               ` David S. Miller
2004-12-28 11:53                 ` Marcelo Tosatti
2004-12-24 16:17           ` Christoph Lameter
2004-12-24 18:31     ` Increase page fault rate by prezeroing V1 [0/3]: Overview Andrea Arcangeli
2005-01-03 17:54       ` Christoph Lameter

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=41D6094C.3040908@yahoo.com.au \
    --to=nickpiggin@yahoo.com.au \
    --cc=agl@us.ibm.com \
    --cc=clameter@sgi.com \
    --cc=holt@sgi.com \
    --cc=linux-ia64@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-mm@vger.kernel.org \
    --cc=tony.luck@intel.com \
    --cc=torvalds@osdl.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).