From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-oi0-f69.google.com (mail-oi0-f69.google.com [209.85.218.69]) by kanga.kvack.org (Postfix) with ESMTP id 6E9496B0314 for ; Tue, 4 Jul 2017 08:59:53 -0400 (EDT) Received: by mail-oi0-f69.google.com with SMTP id 191so33695700oii.4 for ; Tue, 04 Jul 2017 05:59:53 -0700 (PDT) Received: from out30-14.freemail.mail.aliyun.com (out30-14.freemail.mail.aliyun.com. [115.124.30.14]) by mx.google.com with ESMTP id c84si14280698oif.179.2017.07.04.05.59.51 for ; Tue, 04 Jul 2017 05:59:52 -0700 (PDT) Date: Tue, 04 Jul 2017 20:59:25 +0800 From: "zbestahu" Reply-To: "zbestahu" Message-ID: Subject: =?UTF-8?B?UmU6IFJl77yaW1BBVENIXSBtbTogdm1wcmVzc3VyZTogc2ltcGxpZnkgcHJlc3N1cmUgcmF0?= =?UTF-8?B?aW8gY2FsY3VsYXRpb24=?= MIME-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: base64 Sender: owner-linux-mm@kvack.org List-ID: To: Michal Hocko Cc: akpm , minchan , linux-mm , Yue Hu , Anton Vorontsov VGhlIHBhdGNoIGRvZXMgbm90IGNoYW5nZSB0aGUgZnVuY3Rpb24sIHRoZSBleGlzdGluZyBwZXJj ZW50CmNhbGN1bGF0aW9uIHVzaW5nIHNjYWxlIHNob3VsZCBiZSBhYm91dCByb3VuZGluZyB0byBp bnRlZ2VyLCBpdApzZWVtcyB0byBiZSByZWR1bmRhbnQsIHdlIGNhbiBjYWxjdWxhdGUgaXQgZGly ZWN0bHkganVzdCBsaWtlCiJwcmVzc3VyZSA9IG5vdF9yZWxhaW1lZCAqIDEwMCAvIHNjYW5uZWQi LCBubyByb3VuZGluZyBpc3N1ZS4KSXQncyBhbHNvIGJldHRlciBiZWNhdXNlIG9mIHNhdmluZyBz ZXZlcmFsIGFyaXRobWV0aWMgb3BlcmF0aW9ucy4KClNpZ25lZC1vZmYtYnk6IFl1ZSBIdSA8aHV5 dWUyQGNvb2xwYWQuY29tPgotLS0KIG1tL3ZtcHJlc3N1cmUuYyB8IDggKysrLS0tLS0KIDEgZmls ZSBjaGFuZ2VkLCAzIGluc2VydGlvbnMoKyksIDUgZGVsZXRpb25zKC0pCgpkaWZmIC0tZ2l0IGEv bW0vdm1wcmVzc3VyZS5jIGIvbW0vdm1wcmVzc3VyZS5jCmluZGV4IDYwNjM1ODEuLmFhZDFmYjIg MTAwNjQ0Ci0tLSBhL21tL3ZtcHJlc3N1cmUuYworKysgYi9tbS92bXByZXNzdXJlLmMKQEAgLTEx MSw3ICsxMTEsNiBAQCBzdGF0aWMgZW51bSB2bXByZXNzdXJlX2xldmVscyB2bXByZXNzdXJlX2xl dmVsKHVuc2lnbmVkIGxvbmcgcHJlc3N1cmUpCiBzdGF0aWMgZW51bSB2bXByZXNzdXJlX2xldmVs cyB2bXByZXNzdXJlX2NhbGNfbGV2ZWwodW5zaWduZWQgbG9uZyBzY2FubmVkLAogCQkJCQkJICAg IHVuc2lnbmVkIGxvbmcgcmVjbGFpbWVkKQogewotCXVuc2lnbmVkIGxvbmcgc2NhbGUgPSBzY2Fu bmVkICsgcmVjbGFpbWVkOwogCXVuc2lnbmVkIGxvbmcgcHJlc3N1cmUgPSAwOwogCiAJLyoKQEAg LTEyMywxMyArMTIyLDEyIEBAIHN0YXRpYyBlbnVtIHZtcHJlc3N1cmVfbGV2ZWxzIHZtcHJlc3N1 cmVfY2FsY19sZXZlbCh1bnNpZ25lZCBsb25nIHNjYW5uZWQsCiAJCWdvdG8gb3V0OwogCS8qCiAJ ICogV2UgY2FsY3VsYXRlIHRoZSByYXRpbyAoaW4gcGVyY2VudHMpIG9mIGhvdyBtYW55IHBhZ2Vz IHdlcmUKLQkgKiBzY2FubmVkIHZzLiByZWNsYWltZWQgaW4gYSBnaXZlbiB0aW1lIGZyYW1lICh3 aW5kb3cpLiBOb3RlIHRoYXQKLQkgKiB0aW1lIGlzIGluIFZNIHJlY2xhaW1lcidzICJ0aWNrcyIs IGkuZS4gbnVtYmVyIG9mIHBhZ2VzCisJICogdW5zdWNjZXNzZnVsIHJlY2xhaW1lZCB0byBzY2Fu bmVkIGluIGEgZ2l2ZW4gdGltZSBmcmFtZSAod2luZG93KS4KKwkgKiBOb3RlIHRoYXQgdGltZSBp cyBpbiBWTSByZWNsYWltZXIncyAidGlja3MiLCBpLmUuIG51bWJlciBvZiBwYWdlcwogCSAqIHNj YW5uZWQuIFRoaXMgbWFrZXMgaXQgcG9zc2libGUgdG8gc2V0IGRlc2lyZWQgcmVhY3Rpb24gdGlt ZQogCSAqIGFuZCBzZXJ2ZXMgYXMgYSByYXRlbGltaXQuCiAJICovCi0JcHJlc3N1cmUgPSBzY2Fs ZSAtIChyZWNsYWltZWQgKiBzY2FsZSAvIHNjYW5uZWQpOwotCXByZXNzdXJlID0gcHJlc3N1cmUg KiAxMDAgLyBzY2FsZTsKKwlwcmVzc3VyZSA9IChzY2FubmVkIC0gcmVjbGFpbWVkKSAqIDEwMCAv IHNjYW5uZWQ7CiAKIG91dDoKIAlwcl9kZWJ1ZygiJXM6ICUzbHUgIChzOiAlbHUgIHI6ICVsdSlc biIsIF9fZnVuY19fLCBwcmVzc3VyZSwKLS0gCjEuOS4x -- 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 From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pg0-f70.google.com (mail-pg0-f70.google.com [74.125.83.70]) by kanga.kvack.org (Postfix) with ESMTP id 2E01A6B0279 for ; Tue, 4 Jul 2017 09:43:44 -0400 (EDT) Received: by mail-pg0-f70.google.com with SMTP id j186so236034580pge.12 for ; Tue, 04 Jul 2017 06:43:44 -0700 (PDT) Received: from out30-2.freemail.mail.aliyun.com (out30-2.freemail.mail.aliyun.com. [115.124.30.2]) by mx.google.com with ESMTP id w10si14440640pfl.445.2017.07.04.06.43.42 for ; Tue, 04 Jul 2017 06:43:43 -0700 (PDT) Date: Tue, 04 Jul 2017 21:43:39 +0800 From: "zbestahu" Reply-To: "zbestahu" Message-ID: <91b685c4-acee-4ecd-9176-ab95a7172cac.zbestahu@aliyun.com> Subject: =?UTF-8?B?UmU6IFJl77yaW1BBVENIXSBtbTogdm1wcmVzc3VyZTogc2ltcGxpZnkgcHJlc3N1cmUgcmF0?= =?UTF-8?B?aW8gY2FsY3VsYXRpb24=?= MIME-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: base64 Sender: owner-linux-mm@kvack.org List-ID: To: Michal Hocko Cc: akpm , minchan , linux-mm , Yue Hu , Anton Vorontsov TWljaGFsIHdyb3RlOgo+ID4gdGhlIGV4aXN0aW5nIHBlcmNlbnQKPiA+IGNhbGN1bGF0aW9uIHVz aW5nIHNjYWxlIHNob3VsZCBiZSBhYm91dCByb3VuZGluZyB0byBpbnRlZ2UsIGl0Cj4gPiBzZWVt cyB0byBiZSByZWR1bmRhbnQsIHdlIGNhbiBjYWxjdWxhdGUgaXQgZGlyZWN0bHkganVzdCBsaWtl Cj4gPiAicHJlc3N1cmUgPSBub3RfcmVsYWltZWQgKiAxMDAgLyBzY2FubmVkIiwgbm8gcm91bmRp bmcgaXNzdWUuIEFuZAo+ID4gaXQncyBhbHNvIGJldHRlciBiZWNhdXNlIG9mIHNhdmluZyBzZXZl cmFsIGFyaXRobWV0aWMgb3BlcmF0aW9ucy4KCj4gYW5kIHlvdSBoYXZlbid0IGV4cGxhaW5lZCB3 aHkgdGhhdCBjaGFuZ2UgaXMgc28gbXVjaCBiZXR0ZXIgdG8gY2hhbmdlCj4gdGhlIGJlaGF2aW9y LgoKaXQgcmVtb3ZlcyAzIGJlbG93IGFyaXRobWV0aWMgaW5zdHJ1Y3Rpb25zIHNvIGl0IHNob3Vs ZCBiZSBydW5uaW5nIGZhc3Rlci4KYWRkOiBzY2FubmVkICsgcmVjbGFpbWVkCm11bDogc2NhbGUg KiByZWNsYWltZWQKdWRpdjogcmVjbGFpbWVkICogc2NhbGUgL3NjYW5uZWQ= -- 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 From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wr0-f197.google.com (mail-wr0-f197.google.com [209.85.128.197]) by kanga.kvack.org (Postfix) with ESMTP id 720546B02C3 for ; Tue, 4 Jul 2017 09:54:35 -0400 (EDT) Received: by mail-wr0-f197.google.com with SMTP id z81so45656744wrc.2 for ; Tue, 04 Jul 2017 06:54:35 -0700 (PDT) Received: from mx1.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id o23si13404602wro.277.2017.07.04.06.54.33 for (version=TLS1 cipher=AES128-SHA bits=128/128); Tue, 04 Jul 2017 06:54:34 -0700 (PDT) Date: Tue, 4 Jul 2017 15:54:31 +0200 From: Michal Hocko Subject: Re: =?utf-8?B?UmXvvJpbUEFUQ0g=?= =?utf-8?Q?=5D?= mm: vmpressure: simplify pressure ratio calculation Message-ID: <20170704135431.GS14722@dhcp22.suse.cz> References: <91b685c4-acee-4ecd-9176-ab95a7172cac.zbestahu@aliyun.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <91b685c4-acee-4ecd-9176-ab95a7172cac.zbestahu@aliyun.com> Sender: owner-linux-mm@kvack.org List-ID: To: zbestahu Cc: akpm , minchan , linux-mm , Yue Hu , Anton Vorontsov On Tue 04-07-17 21:43:39, zbestahu wrote: > Michal wrote: > > > the existing percent > > > calculation using scale should be about rounding to intege, it > > > seems to be redundant, we can calculate it directly just like > > > "pressure = not_relaimed * 100 / scanned", no rounding issue. And > > > it's also better because of saving several arithmetic operations. > > > and you haven't explained why that change is so much better to change > > the behavior. > > it removes 3 below arithmetic instructions so it should be running faster. > add: scanned + reclaimed > mul: scale * reclaimed > udiv: reclaimed * scale /scanned That part is clear from the diff... What is not clear from the diff is your motivation. This path is not hot (we are in the reclaim which is a slow path) and few extra instructions are acceptable. Sure we can optimize it if the resulting code is working as expected. What I am asking (obviously unsuccessfully) is to describe _why_ it is better. This is a requirement for _each patch_. We are not changing the code "just because I like it more that way". -- Michal Hocko SUSE Labs -- 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