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Re: [PATCH 6/7] BC: kernel memory (core) [message #5759 is a reply to message #5745] Tue, 29 August 2006 18:41 Go to previous messageGo to previous message
Balbir Singh is currently offline  Balbir Singh
Messages: 491
Registered: August 2006
Senior Member
Kirill Korotaev wrote:
> Introduce BC_KMEMSIZE resource which accounts kernel
> objects allocated by task's request.
>
> Reference to BC is kept on struct page or slab object.
> For slabs each struct slab contains a set of pointers
> corresponding objects are charged to.
>
> Allocation charge rules:
> 1. Pages - if allocation is performed with __GFP_BC flag - page
> is charged to current's exec_bc.
> 2. Slabs - kmem_cache may be created with SLAB_BC flag - in this
> case each allocation is charged. Caches used by kmalloc are
> created with SLAB_BC | SLAB_BC_NOCHARGE flags. In this case
> only __GFP_BC allocations are charged.
>

<snip>

> +#define __GFP_BC_LIMIT ((__force gfp_t)0x100000u) /* Charge against BC
> limit */
>

What's _GFP_BC_LIMIT for, could you add the description for that flag?
The comment is not very clear

> +#ifdef CONFIG_BEANCOUNTERS
> + union {
> + struct beancounter *page_bc;
> + } bc;
> +#endif
> };
>
> +#define page_bc(page) ((page)->bc.page_bc)

Minor comment - page->(bc).page_bc has too many repititions of page and bc - see
the Practice of Programming by Kernighan and Pike

I missed the part of why you wanted to have a union (in struct page for bc)?

> const char *bc_rnames[] = {
> + "kmemsize", /* 0 */
> };
>
> static struct hlist_head bc_hash[BC_HASH_SIZE];
> @@ -221,6 +222,8 @@ static void init_beancounter_syslimits(s
> {
> int k;
>
> + bc->bc_parms[BC_KMEMSIZE].limit = 32 * 1024 * 1024;
> +

Can't this be configurable CONFIG_XXX or a #defined constant?

> --- ./mm/mempool.c.bckmem 2006-04-21 11:59:36.000000000 +0400
> +++ ./mm/mempool.c 2006-08-28 12:59:28.000000000 +0400
> @@ -119,6 +119,7 @@ int mempool_resize(mempool_t *pool, int unsigned
> long flags;
>
> BUG_ON(new_min_nr <= 0);
> + gfp_mask &= ~__GFP_BC;
>
> spin_lock_irqsave(&pool->lock, flags);
> if (new_min_nr <= pool->min_nr) {
> @@ -212,6 +213,7 @@ void * mempool_alloc(mempool_t *pool, gf
> gfp_mask |= __GFP_NOMEMALLOC; /* don't allocate emergency
> reserves */
> gfp_mask |= __GFP_NORETRY; /* don't loop in __alloc_pages */
> gfp_mask |= __GFP_NOWARN; /* failures are OK */
> + gfp_mask &= ~__GFP_BC; /* do not charge */
>
> gfp_temp = gfp_mask & ~(__GFP_WAIT|__GFP_IO);
>

Is there any reasn why mempool_xxxx() functions are not charged? Is it because
mempool functions are mostly used from the I/O path?

> --- ./mm/page_alloc.c.bckmem 2006-08-28 12:20:13.000000000 +0400
> +++ ./mm/page_alloc.c 2006-08-28 12:59:28.000000000 +0400
> @@ -40,6 +40,8 @@
> #include <linux/sort.h>
> #include <linux/pfn.h>
>
> +#include <bc/kmem.h>
> +
> #include <asm/tlbflush.h>
> #include <asm/div64.h>
> #include "internal.h"
> @@ -516,6 +518,8 @@ static void __free_pages_ok(struct page if
> (reserved)
> return;
>
> + bc_page_uncharge(page, order);
> +
> kernel_map_pages(page, 1 << order, 0);
> local_irq_save(flags);
> __count_vm_events(PGFREE, 1 << order);
> @@ -799,6 +803,8 @@ static void fastcall free_hot_cold_page(
> if (free_pages_check(page))
> return;
>
> + bc_page_uncharge(page, 0);
> +
> kernel_map_pages(page, 1, 0);
>
> pcp = &zone_pcp(zone, get_cpu())->pcp[cold];
> @@ -1188,6 +1194,11 @@ nopage:
> show_mem();
> }
> got_pg:
> + if ((gfp_mask & __GFP_BC) &&
> + bc_page_charge(page, order, gfp_mask)) {

I wonder if bc_page_charge() should be called bc_page_charge_failed()?
Does it make sense to atleast partially start reclamation here? I know with
bean counters we cannot reclaim from a particular container, but for now
we could kick off kswapd() or call shrink_all_memory() inline (Dave's patches do
this to shrink memory from the particular cpuset). Or do you want to leave this
slot open for later?

> + __free_pages(page, order);
> + page = NULL;
> + }


--

Balbir Singh,
Linux Technology Center,
IBM Software Labs

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