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Date: Tue, 23 Mar 2010 20:40:29 +0800
From: jing zhang <zj.barak@...il.com>
To: tytso@....edu
Cc: linux-ext4 <linux-ext4@...r.kernel.org>,
Andreas Dilger <adilger@....com>,
Dave Kleikamp <shaggy@...ux.vnet.ibm.com>
Subject: Re: [PATCH] ext4: remove unnecessary operation in
ext4_mb_regular_allocator()
2010/3/23, tytso@....edu <tytso@....edu>:
> On Mon, Mar 22, 2010 at 10:35:54PM +0800, jing zhang wrote:
>> From: Jing Zhang <zj.barak@...il.com>
>>
>> Date: Mon Mar 22 22:20:38 2010
>>
>> 1, In one of the hot functions in mballoc.c, unnecessary operation on
>> struct ext4_group_desc *desc;
>> is removed.
---
diff --git a/linux-2.6.32/fs/ext4/mballoc.c b/ext4_mm_leak/mballoc5.c
index bba1282..fb18199 100644
--- a/linux-2.6.32/fs/ext4/mballoc.c
+++ b/ext4_mm_leak/mballoc5.c
@@ -2027,7 +2027,6 @@ repeat:
for (i = 0; i < ngroups; group++, i++) {
struct ext4_group_info *grp;
- struct ext4_group_desc *desc;
if (group == ngroups)
group = 0;
@@ -2050,7 +2049,6 @@ repeat:
}
ac->ac_groups_scanned++;
- desc = ext4_get_group_desc(sb, group, NULL);
if (cr == 0)
ext4_mb_simple_scan_group(ac, &e4b);
else if (cr == 1 &&
>> 2, Unlike spin_lock() and spin_unlock(), ext4_mb_load_buddy() is
>> companied by ext4_mb_release_desc. And it is hard, at least for me, to
>> get sure that ext4_mb_release_desc has little to do with struct
>> ext4_group_desc, and for those readers as well, whose native language
>> is not English. It seems the choice includes
>> ext4_mb_release_buddy
>> ext4_mb_put_buddy
>> ext4_mb_unload_buddy
>> and I like the last one.
---
diff --git a/linux-2.6.32/fs/ext4/mballoc.c b/ext4_mm_leak/mballoc4.c
index bba1282..45d78a9 100644
--- a/linux-2.6.32/fs/ext4/mballoc.c
+++ b/ext4_mm_leak/mballoc4.c
@@ -1150,7 +1150,7 @@ err:
return ret;
}
-static void ext4_mb_release_desc(struct ext4_buddy *e4b)
+static void ext4_mb_unload_buddy(struct ext4_buddy *e4b)
{
if (e4b->bd_bitmap_page)
page_cache_release(e4b->bd_bitmap_page);
@@ -1618,7 +1618,7 @@ int ext4_mb_try_best_found(struct
ext4_allocation_context *ac,
}
ext4_unlock_group(ac->ac_sb, group);
- ext4_mb_release_desc(e4b);
+ ext4_mb_unload_buddy(e4b);
return 0;
}
@@ -1674,7 +1674,7 @@ int ext4_mb_find_by_goal(struct
ext4_allocation_context *ac,
ext4_mb_use_best_found(ac, e4b);
}
ext4_unlock_group(ac->ac_sb, group);
- ext4_mb_release_desc(e4b);
+ ext4_mb_unload_buddy(e4b);
return 0;
}
@@ -2045,7 +2045,7 @@ repeat:
if (!ext4_mb_good_group(ac, group, cr)) {
/* someone did allocation from this group */
ext4_unlock_group(sb, group);
- ext4_mb_release_desc(&e4b);
+ ext4_mb_unload_buddy(&e4b);
continue;
}
@@ -2060,7 +2060,7 @@ repeat:
ext4_mb_complex_scan_group(ac, &e4b);
ext4_unlock_group(sb, group);
- ext4_mb_release_desc(&e4b);
+ ext4_mb_unload_buddy(&e4b);
if (ac->ac_status != AC_STATUS_CONTINUE)
break;
@@ -2150,7 +2150,7 @@ static int ext4_mb_seq_groups_show(struct
seq_file *seq, void *v)
ext4_lock_group(sb, group);
memcpy(&sg, ext4_get_group_info(sb, group), i);
ext4_unlock_group(sb, group);
- ext4_mb_release_desc(&e4b);
+ ext4_mb_unload_buddy(&e4b);
seq_printf(seq, "#%-5u: %-5u %-5u %-5u [", group, sg.info.bb_free,
sg.info.bb_fragments, sg.info.bb_first_free);
@@ -2567,7 +2567,7 @@ static void release_blocks_on_commit(journal_t
*journal, transaction_t *txn)
sb_issue_discard(sb, discard_block, entry->count);
kmem_cache_free(ext4_free_ext_cachep, entry);
- ext4_mb_release_desc(&e4b);
+ ext4_mb_unload_buddy(&e4b);
}
mb_debug(1, "freed %u blocks in %u structures\n", count, count2);
@@ -3692,7 +3692,7 @@ out:
ext4_unlock_group(sb, group);
if (ac)
kmem_cache_free(ext4_ac_cachep, ac);
- ext4_mb_release_desc(&e4b);
+ ext4_mb_unload_buddy(&e4b);
put_bh(bitmap_bh);
return free;
}
@@ -3796,7 +3796,7 @@ repeat:
if (bitmap_bh == NULL) {
ext4_error(sb, __func__, "Error in reading block "
"bitmap for %u", group);
- ext4_mb_release_desc(&e4b);
+ ext4_mb_unload_buddy(&e4b);
continue;
}
@@ -3805,7 +3805,7 @@ repeat:
ext4_mb_release_inode_pa(&e4b, bitmap_bh, pa, ac);
ext4_unlock_group(sb, group);
- ext4_mb_release_desc(&e4b);
+ ext4_mb_unload_buddy(&e4b);
put_bh(bitmap_bh);
list_del(&pa->u.pa_tmp_list);
@@ -4069,7 +4069,7 @@ ext4_mb_discard_lg_preallocations(struct super_block *sb,
ext4_mb_release_group_pa(&e4b, pa, ac);
ext4_unlock_group(sb, group);
- ext4_mb_release_desc(&e4b);
+ ext4_mb_unload_buddy(&e4b);
list_del(&pa->u.pa_tmp_list);
call_rcu(&(pa)->u.pa_rcu, ext4_mb_pa_callback);
}
@@ -4570,7 +4570,7 @@ do_more:
atomic_add(count, &sbi->s_flex_groups[flex_group].free_blocks);
}
- ext4_mb_release_desc(&e4b);
+ ext4_mb_unload_buddy(&e4b);
*freed += count;
> Please separate things like this into two separate patches; it makes
> them much easier to review.
>
> Thanks,
>
> - Ted
>
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