From: Gautham R Shenoy <ego@linux.vnet.ibm.com>
To: Nicholas Piggin <npiggin@gmail.com>
Cc: linuxppc-dev@lists.ozlabs.org,
Gautham R Shenoy <ego@linux.vnet.ibm.com>,
Vaidyanathan Srinivasan <svaidy@linux.vnet.ibm.com>
Subject: Re: [PATCH 2/8] powerpc/64s: stop using bit in HSPRG0 to test winkle
Date: Thu, 16 Mar 2017 16:44:38 +0530 [thread overview]
Message-ID: <20170316111438.GA16462@in.ibm.com> (raw)
In-Reply-To: <20170314092349.10981-3-npiggin@gmail.com>
Hi Nick,
On Tue, Mar 14, 2017 at 07:23:43PM +1000, Nicholas Piggin wrote:
> The POWER8 idle code has a neat trick of programming the power on engine
> to restore a low bit into HSPRG0, so idle wakeup code can test and see
> if it has been programmed this way and therefore lost all state, and
> avoiding the expensive full restore if not.
>
> However this messes with our r13 PACA pointer, and requires HSPRG0 to
> be written to throughout the exception handlers and idle wakeup, rather
> than just once on kernel entry.
>
> Remove this complexity and assume winkle sleeps always require a state
> restore. This speedup is later re-introduced by counting per-core winkles
> and setting a bitmap of threads with state loss when all are in winkle.
>
Looks good to me.
> Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Reviewed-by: Gautham R. Shenoy <ego@linux.vnet.ibm.com>
--
Thanks and Regards
gautham.
next prev parent reply other threads:[~2017-03-16 11:14 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-03-14 9:23 [PATCH 0/8] idle fixes and changes for POWER8 and POWER9 Nicholas Piggin
2017-03-14 9:23 ` [PATCH 1/8] powerpc/64s: move remaining system reset idle code into idle_book3s.S Nicholas Piggin
2017-03-14 9:23 ` [PATCH 2/8] powerpc/64s: stop using bit in HSPRG0 to test winkle Nicholas Piggin
2017-03-16 11:14 ` Gautham R Shenoy [this message]
2017-03-14 9:23 ` [PATCH 3/8] powerpc/64s: use alternative feature patching Nicholas Piggin
2017-03-16 11:21 ` Gautham R Shenoy
2017-03-14 9:23 ` [PATCH 4/8] powerpc/64s: fix POWER9 machine check handler from stop state Nicholas Piggin
2017-03-16 12:40 ` Mahesh Jagannath Salgaonkar
2017-03-16 13:05 ` Nicholas Piggin
2017-03-16 13:19 ` Gautham R Shenoy
2017-03-20 5:22 ` Mahesh Jagannath Salgaonkar
2017-03-17 2:49 ` Nicholas Piggin
2017-03-17 5:15 ` Nicholas Piggin
2017-03-14 9:23 ` [PATCH 5/8] powerpc/64s: use PACA_THREAD_IDLE_STATE only in POWER8 Nicholas Piggin
2017-03-16 11:54 ` Gautham R Shenoy
2017-03-16 12:16 ` Nicholas Piggin
2017-03-14 9:23 ` [PATCH 6/8] powerpc/64s: idle expand usable core idle state bits Nicholas Piggin
2017-03-16 12:10 ` Gautham R Shenoy
2017-03-14 9:23 ` [PATCH 7/8] powerpc/64s: idle do not hold reservation longer than required Nicholas Piggin
2017-03-16 12:43 ` Gautham R Shenoy
2017-03-16 12:55 ` Nicholas Piggin
2017-03-14 9:23 ` [PATCH 8/8] powerpc/64s: idle POWER8 avoid full state loss recovery when possible Nicholas Piggin
2017-03-16 16:12 ` Gautham R Shenoy
2017-03-17 5:24 ` Nicholas Piggin
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