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Date: Wed, 19 Jan 2022 13:12:29 +0000 From: Praveen Kannoju <praveen.kannoju@...cle.com> To: Jason Gunthorpe <jgg@...pe.ca> CC: Leon Romanovsky <leon@...nel.org>, Santosh Shilimkar <santosh.shilimkar@...cle.com>, "David S . Miller" <davem@...emloft.net>, "kuba@...nel.org" <kuba@...nel.org>, "netdev@...r.kernel.org" <netdev@...r.kernel.org>, "linux-rdma@...r.kernel.org" <linux-rdma@...r.kernel.org>, "rds-devel@....oracle.com" <rds-devel@....oracle.com>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, Rama Nichanamatlu <rama.nichanamatlu@...cle.com>, Rajesh Sivaramasubramaniom <rajesh.sivaramasubramaniom@...cle.com> Subject: RE: [PATCH RFC] rds: ib: Reduce the contention caused by the asynchronous workers to flush the mr pool -----Original Message----- From: Jason Gunthorpe [mailto:jgg@...pe.ca] Sent: 19 January 2022 06:35 PM To: Praveen Kannoju <praveen.kannoju@...cle.com> Cc: Leon Romanovsky <leon@...nel.org>; Santosh Shilimkar <santosh.shilimkar@...cle.com>; David S . Miller <davem@...emloft.net>; kuba@...nel.org; netdev@...r.kernel.org; linux-rdma@...r.kernel.org; rds-devel@....oracle.com; linux-kernel@...r.kernel.org; Rama Nichanamatlu <rama.nichanamatlu@...cle.com>; Rajesh Sivaramasubramaniom <rajesh.sivaramasubramaniom@...cle.com> Subject: Re: [PATCH RFC] rds: ib: Reduce the contention caused by the asynchronous workers to flush the mr pool On Wed, Jan 19, 2022 at 11:46:16AM +0000, Praveen Kannoju wrote: > 6. Jason, the only function "rds_ib_free_mr" which accesses the > introduced bool variable "flush_ongoing" to spawn a flush worker does > not crucially impact the availability of MR's, because the flush > happens from allocation path as well when necessary. Hence the > Load-store ordering is not essentially needed here, because of which > we chose smp_rmb() and smp_wmb() over smp_load_acquire() and > smp_store_release(). That seems like a confusing statement, you added barriers which do the same things as acquire/release then say you didn't need acquire release? I think this is using barriers wrong. Jason Jason, Yes, we are using the barriers. I was justifying the usage of smp_rmb() and smp_wmb() over smp_load_acquire() and smp_store_release() in the patch.
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