Messages in this thread | | | From | Sunil Kovvuri Goutham <> | Subject | RE: [EXT] [PATCH 07/22] net: octeontx2: Use alloc_ordered_workqueue() to create ordered workqueues | Date | Fri, 21 Apr 2023 06:16:49 +0000 |
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> -----Original Message----- > From: Tejun Heo <htejun@gmail.com> On Behalf Of Tejun Heo > Sent: Friday, April 21, 2023 8:21 AM > To: jiangshanlai@gmail.com > Cc: linux-kernel@vger.kernel.org; kernel-team@meta.com; Tejun Heo > <tj@kernel.org>; David S. Miller <davem@davemloft.net>; Eric Dumazet > <edumazet@google.com>; Jakub Kicinski <kuba@kernel.org>; Paolo Abeni > <pabeni@redhat.com>; Sunil Kovvuri Goutham <sgoutham@marvell.com>; > Ratheesh Kannoth <rkannoth@marvell.com>; Srujana Challa > <schalla@marvell.com>; Geethasowjanya Akula <gakula@marvell.com>; > netdev@vger.kernel.org > Subject: [EXT] [PATCH 07/22] net: octeontx2: Use alloc_ordered_workqueue() > to create ordered workqueues > > External Email > > ---------------------------------------------------------------------- > BACKGROUND > ========== > > When multiple work items are queued to a workqueue, their execution order > doesn't match the queueing order. They may get executed in any order and > simultaneously. When fully serialized execution - one by one in the queueing > order - is needed, an ordered workqueue should be used which can be created > with alloc_ordered_workqueue(). > > However, alloc_ordered_workqueue() was a later addition. Before it, an ordered > workqueue could be obtained by creating an UNBOUND workqueue with > @max_active==1. This originally was an implementation side-effect which was > broken by 4c16bd327c74 ("workqueue: restore WQ_UNBOUND/max_active==1 > to be ordered"). Because there were users that depended on the ordered > execution, > 5c0338c68706 ("workqueue: restore WQ_UNBOUND/max_active==1 to be > ordered") made workqueue allocation path to implicitly promote UNBOUND > workqueues w/ > @max_active==1 to ordered workqueues. > > While this has worked okay, overloading the UNBOUND allocation interface this > way creates other issues. It's difficult to tell whether a given workqueue actually > needs to be ordered and users that legitimately want a min concurrency level wq > unexpectedly gets an ordered one instead. With planned UNBOUND workqueue > updates to improve execution locality and more prevalence of chiplet designs > which can benefit from such improvements, this isn't a state we wanna be in > forever. > > This patch series audits all callsites that create an UNBOUND workqueue w/ > @max_active==1 and converts them to alloc_ordered_workqueue() as > necessary. > > WHAT TO LOOK FOR > ================ > > The conversions are from > > alloc_workqueue(WQ_UNBOUND | flags, 1, args..) > > to > > alloc_ordered_workqueue(flags, args...) > > which don't cause any functional changes. If you know that fully ordered > execution is not ncessary, please let me know. I'll drop the conversion and > instead add a comment noting the fact to reduce confusion while conversion is > in progress. > > If you aren't fully sure, it's completely fine to let the conversion through. The > behavior will stay exactly the same and we can always reconsider later. > > As there are follow-up workqueue core changes, I'd really appreciate if the > patch can be routed through the workqueue tree w/ your acks. Thanks. > > Signed-off-by: Tejun Heo <tj@kernel.org> > Cc: "David S. Miller" <davem@davemloft.net> > Cc: Eric Dumazet <edumazet@google.com> > Cc: Jakub Kicinski <kuba@kernel.org> > Cc: Paolo Abeni <pabeni@redhat.com> > Cc: Sunil Goutham <sgoutham@marvell.com> > Cc: Ratheesh Kannoth <rkannoth@marvell.com> > Cc: Srujana Challa <schalla@marvell.com> > Cc: Geetha sowjanya <gakula@marvell.com> > Cc: netdev@vger.kernel.org > --- > drivers/net/ethernet/marvell/octeontx2/af/rvu.c | 5 ++--- > .../net/ethernet/marvell/octeontx2/nic/otx2_pf.c | 13 +++++-------- > .../net/ethernet/marvell/octeontx2/nic/otx2_vf.c | 5 ++--- > 3 files changed, 9 insertions(+), 14 deletions(-) > Reviewed-by: Sunil Goutham <sgoutham@marvell.com>
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