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charset="us-ascii" Content-ID: <441ECF679B6B564EA443DDA909A09D4A@namprd10.prod.outlook.com> Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-OriginatorOrg: oracle.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-AuthSource: SJ0PR10MB4688.namprd10.prod.outlook.com X-MS-Exchange-CrossTenant-Network-Message-Id: bd5380c0-4831-4727-4058-08d8cea8f462 X-MS-Exchange-CrossTenant-originalarrivaltime: 11 Feb 2021 16:20:32.1219 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: 4e2c6054-71cb-48f1-bd6c-3a9705aca71b X-MS-Exchange-CrossTenant-mailboxtype: HOSTED X-MS-Exchange-CrossTenant-userprincipalname: QV2j7oOZQ+WepypBqrCZHYJBawZx3w61zsvAJNjaFXMwRcQiJLwWmGpeCSB6pd2eFJI1oaOXvf4wlAd9wqYA8A== X-MS-Exchange-Transport-CrossTenantHeadersStamped: BY5PR10MB4131 X-Proofpoint-Virus-Version: vendor=nai engine=6200 definitions=9892 signatures=668683 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 suspectscore=0 adultscore=0 mlxlogscore=999 malwarescore=0 bulkscore=0 phishscore=0 spamscore=0 mlxscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2009150000 definitions=main-2102110136 X-Proofpoint-Virus-Version: vendor=nai engine=6200 definitions=9892 signatures=668683 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 priorityscore=1501 malwarescore=0 spamscore=0 lowpriorityscore=0 phishscore=0 adultscore=0 impostorscore=0 suspectscore=0 mlxscore=0 clxscore=1015 mlxlogscore=999 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2009150000 definitions=main-2102110136 Precedence: bulk List-ID: X-Mailing-List: linux-nfs@vger.kernel.org > On Feb 11, 2021, at 4:12 AM, Mel Gorman wro= te: >=20 > On Wed, Feb 10, 2021 at 10:58:37PM +0000, Chuck Lever wrote: >>> Not in the short term due to bug load and other obligations. >>>=20 >>> The original series had "mm, page_allocator: Only use per-cpu allocator >>> for irq-safe requests" but that was ultimately rejected because softirq= s >>> were affected so it would have to be done without that patch. >>>=20 >>> The last patch can be rebased easily enough but it only batch allocates >>> order-0 pages. It's also only build tested and could be completely >>> miserable in practice and as I didn't even try boot test let, let alone >>> actually test it, it could be a giant pile of crap. To make high orders >>> work, it would need significant reworking but if the API showed even >>> partial benefit, it might motiviate someone to reimplement the bulk >>> interfaces to perform better. >>>=20 >>> Rebased diff, build tested only, might not even work >>=20 >> Thanks, Mel, for kicking off a forward port. >>=20 >> It compiles. I've added a patch to replace the page allocation loop >> in svc_alloc_arg() with a call to alloc_pages_bulk(). >>=20 >> The server system deadlocks pretty quickly with any NFS traffic. Based >> on some initial debugging, it appears that a pcplist is getting corrupte= d >> and this causes the list_del() in __rmqueue_pcplist() to fail during a >> a call to alloc_pages_bulk(). >>=20 >=20 > Parameters to __rmqueue_pcplist are garbage as the parameter order change= d. > I'm surprised it didn't blow up in a spectacular fashion. Again, this > hasn't been near any testing and passing a list with high orders to > free_pages_bulk() will corrupt lists too. Mostly it's a curiousity to see > if there is justification for reworking the allocator to fundamentally > deal in batches and then feed batches to pcp lists and the bulk allocator > while leaving the normal GFP API as single page "batches". While that > would be ideal, it's relatively high risk for regressions. There is still > some scope for adding a basic bulk allocator before considering a major > refactoring effort. >=20 > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index f8353ea7b977..8f3fe7de2cf7 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -5892,7 +5892,7 @@ __alloc_pages_bulk_nodemask(gfp_t gfp_mask, unsigne= d int order, > pcp_list =3D &pcp->lists[migratetype]; >=20 > while (nr_pages) { > - page =3D __rmqueue_pcplist(zone, gfp_mask, migratetype, > + page =3D __rmqueue_pcplist(zone, migratetype, alloc_flags, > pcp, pcp_list); > if (!page) > break; The NFS server is considerably more stable now. Thank you! I confirmed that my patch is requesting and getting multiple pages. The new NFSD code and the API seem to be working as expected. The results are stunning. Each svc_alloc_arg() call here allocates 65 pages to satisfy a 256KB NFS READ request. Before: nfsd-972 [000] 584.513817: funcgraph_entry: + 35.385 u= s | svc_alloc_arg(); nfsd-979 [002] 584.513870: funcgraph_entry: + 29.051 u= s | svc_alloc_arg(); nfsd-980 [001] 584.513951: funcgraph_entry: + 29.178 u= s | svc_alloc_arg(); nfsd-983 [000] 584.514014: funcgraph_entry: + 29.211 u= s | svc_alloc_arg(); nfsd-976 [002] 584.514059: funcgraph_entry: + 29.315 u= s | svc_alloc_arg(); nfsd-974 [001] 584.514127: funcgraph_entry: + 29.237 u= s | svc_alloc_arg(); After: nfsd-977 [002] 87.049425: funcgraph_entry: 4.293 us= | svc_alloc_arg(); nfsd-981 [000] 87.049478: funcgraph_entry: 4.059 us= | svc_alloc_arg(); nfsd-988 [001] 87.049549: funcgraph_entry: 4.474 us= | svc_alloc_arg(); nfsd-983 [003] 87.049612: funcgraph_entry: 3.819 us= | svc_alloc_arg(); nfsd-976 [000] 87.049619: funcgraph_entry: 3.869 us= | svc_alloc_arg(); nfsd-980 [002] 87.049738: funcgraph_entry: 4.124 us= | svc_alloc_arg(); nfsd-975 [000] 87.049769: funcgraph_entry: 3.734 us= | svc_alloc_arg(); There appears to be little cost change for single-page allocations using the bulk allocator (nr_pages=3D1): Before: nfsd-985 [003] 572.324517: funcgraph_entry: 0.332 us= | svc_alloc_arg(); nfsd-986 [001] 572.324531: funcgraph_entry: 0.311 us= | svc_alloc_arg(); nfsd-985 [003] 572.324701: funcgraph_entry: 0.311 us= | svc_alloc_arg(); nfsd-986 [001] 572.324727: funcgraph_entry: 0.424 us= | svc_alloc_arg(); nfsd-985 [003] 572.324760: funcgraph_entry: 0.332 us= | svc_alloc_arg(); nfsd-986 [001] 572.324786: funcgraph_entry: 0.390 us= | svc_alloc_arg(); After: nfsd-989 [002] 75.043226: funcgraph_entry: 0.322 us= | svc_alloc_arg(); nfsd-988 [001] 75.043436: funcgraph_entry: 0.368 us= | svc_alloc_arg(); nfsd-989 [002] 75.043464: funcgraph_entry: 0.424 us= | svc_alloc_arg(); nfsd-988 [001] 75.043490: funcgraph_entry: 0.317 us= | svc_alloc_arg(); nfsd-989 [002] 75.043517: funcgraph_entry: 0.425 us= | svc_alloc_arg(); nfsd-988 [001] 75.050025: funcgraph_entry: 0.407 us= | svc_alloc_arg(); -- Chuck Lever