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Modify pool page header allocation strategy as follows:

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In addition to current one (i.e., don't wast so large part of the page),
- if the header fitsin the page without wasting any items, put it there.
- don't put the header in the page if it may consume rather big item.

For example, on i386, header is now allocated in the page for the pools
like fdescpl or sigapl, and allocated off the page for the pools like
buf1k or buf2k.
This commit is contained in:
enami 2004-02-22 00:19:48 +00:00
parent 859077437c
commit 06107df871
1 changed files with 20 additions and 12 deletions
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32
sys/kern/subr_pool.c
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@ -1,4 +1,4 @@
/* $NetBSD: subr_pool.c,v 1.91 2004/01/16 12:47:37 yamt Exp $ */
/* $NetBSD: subr_pool.c,v 1.92 2004/02/22 00:19:48 enami Exp $ */
/*-
* Copyright (c) 1997, 1999, 2000 The NetBSD Foundation, Inc.
@ -38,7 +38,7 @@
*/
#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: subr_pool.c,v 1.91 2004/01/16 12:47:37 yamt Exp $");
__KERNEL_RCSID(0, "$NetBSD: subr_pool.c,v 1.92 2004/02/22 00:19:48 enami Exp $");
#include "opt_pool.h"
#include "opt_poollog.h"
@ -367,6 +367,7 @@ pool_init(struct pool *pp, size_t size, u_int align, u_int ioff, int flags,
const char *wchan, struct pool_allocator *palloc)
{
int off, slack;
size_t trysize, phsize;
#ifdef POOL_DIAGNOSTIC
/*
@ -458,16 +459,26 @@ pool_init(struct pool *pp, size_t size, u_int align, u_int ioff, int flags,
/*
* Decide whether to put the page header off page to avoid
* wasting too large a part of the page. Off-page page headers
* go on a hash table, so we can match a returned item
* with its header based on the page address.
* We use 1/16 of the page size as the threshold (XXX: tune)
* wasting too large a part of the page or too big item.
* Off-page page headers go on a hash table, so we can match
* a returned item with its header based on the page address.
* We use 1/16 of the page size and about 8 times of the item
* size as the threshold (XXX: tune)
*
* However, we'll put the header into the page if we can put
* it without wasting any items.
*
* Silently enforce `0 <= ioff < align'.
*/
if (pp->pr_size < palloc->pa_pagesz/16) {
pp->pr_itemoffset = ioff %= align;
/* See the comment below about reserved bytes. */
trysize = palloc->pa_pagesz - ((align - ioff) % align);
phsize = ALIGN(sizeof(struct pool_item_header));
if (pp->pr_size < MIN(palloc->pa_pagesz / 16, phsize << 3) ||
trysize / pp->pr_size == (trysize - phsize) / pp->pr_size) {
/* Use the end of the page for the page header */
pp->pr_roflags |= PR_PHINPAGE;
pp->pr_phoffset = off = palloc->pa_pagesz -
ALIGN(sizeof(struct pool_item_header));
pp->pr_phoffset = off = palloc->pa_pagesz - phsize;
} else {
/* The page header will be taken from our page header pool */
pp->pr_phoffset = 0;
@ -479,10 +490,7 @@ pool_init(struct pool *pp, size_t size, u_int align, u_int ioff, int flags,
* Alignment is to take place at `ioff' within the item. This means
* we must reserve up to `align - 1' bytes on the page to allow
* appropriate positioning of each item.
*
* Silently enforce `0 <= ioff < align'.
*/
pp->pr_itemoffset = ioff = ioff % align;
pp->pr_itemsperpage = (off - ((align - ioff) % align)) / pp->pr_size;
KASSERT(pp->pr_itemsperpage != 0);