From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751661AbbIOAtO (ORCPT ); Mon, 14 Sep 2015 20:49:14 -0400 Received: from mail-pa0-f43.google.com ([209.85.220.43]:33350 "EHLO mail-pa0-f43.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751355AbbIOAtM (ORCPT ); Mon, 14 Sep 2015 20:49:12 -0400 Date: Tue, 15 Sep 2015 09:49:57 +0900 From: Sergey Senozhatsky To: Vitaly Wool Cc: minchan@kernel.org, sergey.senozhatsky@gmail.com, ddstreet@ieee.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH 0/3] allow zram to use zbud as underlying allocator Message-ID: <20150915004957.GA1860@swordfish> References: <20150914154901.92c5b7b24e15f04d8204de18@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20150914154901.92c5b7b24e15f04d8204de18@gmail.com> User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On (09/14/15 15:49), Vitaly Wool wrote: > While using ZRAM on a small RAM footprint devices, together with KSM, > I ran into several occasions when moving pages from compressed swap back > into the "normal" part of RAM caused significant latencies in system operation. > By using zbud I lose in compression ratio but gain in determinism, lower > latencies and lower fragmentation, so in the coming patches I tried to > generalize what I've done to enable zbud for zram so far. > do you have CONFIG_PGTABLE_MAPPING enabled or disabled? or kmap_atomic/memcpy/kunmap_atomic is not the root cause here? can you provide more details please? -ss