From mboxrd@z Thu Jan 1 00:00:00 1970 From: Johannes Weiner Subject: [patch 06/12] mm: memcontrol: simplify move precharge function Date: Mon, 16 Jun 2014 15:54:26 -0400 Message-ID: <1402948472-8175-7-git-send-email-hannes@cmpxchg.org> References: <1402948472-8175-1-git-send-email-hannes@cmpxchg.org> Return-path: DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=cmpxchg.org; s=zene; h=References:In-Reply-To:Message-Id:Date:Subject:Cc:To:From; bh=MnCgxo/nlfJsciu+lw6bvG3Al+vDmk6QgjEaI5EnYwo=; b=BATBUb1sQ5czRyL+linT8yFk/VzNpP1dfIZ2Uj+nl1QMRV5mjgVtBFxPCIvZ84waS4FftyQS7UncXOdf6Ds9BSj//EL9GC37vbyHuN/bG8Cgm3KAhrBsD5wyJ/OcBrCJf5CU3Nn8idGZqFjZXOunYjdqCmc94CHvcFZ1MgRsF+Q=; In-Reply-To: <1402948472-8175-1-git-send-email-hannes@cmpxchg.org> Sender: owner-linux-mm@kvack.org List-ID: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Andrew Morton Cc: Michal Hocko , Hugh Dickins , Tejun Heo , Vladimir Davydov , cgroups@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org The move precharge function does some baroque things: it tries raw res_counter charging of the entire amount first, and then falls back to a loop of one-by-one charges, with checks for pending signals and cond_resched() batching. Just use mem_cgroup_try_charge() without __GFP_WAIT for the first bulk charge attempt. In the one-by-one loop, remove the signal check (this is already checked in try_charge), and simply call cond_resched() after every charge - it's not that expensive. Signed-off-by: Johannes Weiner --- mm/memcontrol.c | 51 +++++++++++++++++---------------------------------- 1 file changed, 17 insertions(+), 34 deletions(-) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 9c646b9b56f4..3d9df94896a7 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -6372,55 +6372,38 @@ static void mem_cgroup_css_free(struct cgroup_subsys_state *css) #ifdef CONFIG_MMU /* Handlers for move charge at task migration. */ -#define PRECHARGE_COUNT_AT_ONCE 256 static int mem_cgroup_do_precharge(unsigned long count) { - int ret = 0; - int batch_count = PRECHARGE_COUNT_AT_ONCE; - struct mem_cgroup *memcg = mc.to; + int ret; - if (mem_cgroup_is_root(memcg)) { + if (mem_cgroup_is_root(mc.to)) { mc.precharge += count; /* we don't need css_get for root */ return ret; } - /* try to charge at once */ - if (count > 1) { - struct res_counter *dummy; - /* - * "memcg" cannot be under rmdir() because we've already checked - * by cgroup_lock_live_cgroup() that it is not removed and we - * are still under the same cgroup_mutex. So we can postpone - * css_get(). - */ - if (res_counter_charge(&memcg->res, PAGE_SIZE * count, &dummy)) - goto one_by_one; - if (do_swap_account && res_counter_charge(&memcg->memsw, - PAGE_SIZE * count, &dummy)) { - res_counter_uncharge(&memcg->res, PAGE_SIZE * count); - goto one_by_one; - } + + /* Try a single bulk charge without reclaim first */ + ret = mem_cgroup_try_charge(mc.to, GFP_KERNEL & ~__GFP_WAIT, + count, false); + if (!ret) { mc.precharge += count; return ret; } -one_by_one: - /* fall back to one by one charge */ + + /* Try charges one by one with reclaim */ while (count--) { - if (signal_pending(current)) { - ret = -EINTR; - break; - } - if (!batch_count--) { - batch_count = PRECHARGE_COUNT_AT_ONCE; - cond_resched(); - } - ret = mem_cgroup_try_charge(memcg, GFP_KERNEL, 1, false); + ret = mem_cgroup_try_charge(mc.to, GFP_KERNEL, 1, false); + /* + * In case of failure, any residual charges against + * mc.to will be dropped by mem_cgroup_clear_mc() + * later on. + */ if (ret) - /* mem_cgroup_clear_mc() will do uncharge later */ return ret; mc.precharge++; + cond_resched(); } - return ret; + return 0; } /** -- 2.0.0 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org