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charset="us-ascii" Content-ID: <49F27AFB6826CB4B9F8061DC970E5C56@namprd15.prod.outlook.com> Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-MS-Exchange-CrossTenant-Network-Message-Id: cfb5dd30-98b2-4431-7631-08d755c4f00b X-MS-Exchange-CrossTenant-originalarrivaltime: 21 Oct 2019 01:21:02.6827 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: 8ae927fe-1255-47a7-a2af-5f3a069daaa2 X-MS-Exchange-CrossTenant-mailboxtype: HOSTED X-MS-Exchange-CrossTenant-userprincipalname: EQq9x6MHidoBSAbcUdA3XxqQbF7wgEE0A7d/cYkJWjSlVJk5sPInPzKhUFD9tFJH X-MS-Exchange-Transport-CrossTenantHeadersStamped: BN8PR15MB2577 X-OriginatorOrg: fb.com X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.95,1.0.8 definitions=2019-10-20_06:2019-10-18,2019-10-20 signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 suspectscore=0 mlxscore=0 clxscore=1015 mlxlogscore=864 impostorscore=0 adultscore=0 malwarescore=0 lowpriorityscore=0 bulkscore=0 priorityscore=1501 spamscore=0 phishscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-1908290000 definitions=main-1910210008 X-FB-Internal: deliver Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, Oct 20, 2019 at 10:51:10PM +0000, Christopher Lameter wrote: > On Thu, 17 Oct 2019, Roman Gushchin wrote: >=20 > > Currently s8 type is used for per-cpu caching of per-node statistics. > > It works fine because the overfill threshold can't exceed 125. > > > > But if some counters are in bytes (and the next commit in the series > > will convert slab counters to bytes), it's not gonna work: > > value in bytes can easily exceed s8 without exceeding the threshold > > converted to bytes. So to avoid overfilling per-cpu caches and breaking > > vmstats correctness, let's use s32 instead. >=20 > Actually this is inconsistenct since the other counters are all used to > account for pages. Some of the functions in use for the page counters wil= l > no longer make sense. inc/dec_node_state() etc. Actually I tried to implement what Johannes suggested earlier and convert all counters to bytes, but it looked like it can lead to a significant performance hit on 32bit platforms, as I'd need to replace all atomic_long_= t with atomic64_t. Also, to make the code look good, I'd need to convert all counters to bytes (and atomic64_t): zone stats, vmevents, etc. So I gave up relatively quickly. Maybe it's a good long-term plan, but as now it doesn't really look as an obviously good think to do. I'm fully open to any suggestions here.