linux-kernel - Re: apparent regressions from TLB range flushing page set

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Message-Id: <50349BF6020000780008A4C6@nat28.tlf.novell.com>
Date:	Wed, 22 Aug 2012 08:44:38 +0100
From:	"Jan Beulich" <jbeulich@...e.com>
To:	<alex.shi@...el.com>
Cc:	<konrad.wilk@...cle.com>, <linux-kernel@...r.kernel.org>,
	<hpa@...or.com>
Subject: Re: apparent regressions from TLB range flushing page set

>>> Alex Shi <alex.shi@...el.com> 08/22/12 5:27 AM >>>
>> Second, the UV code doesn't flush the full range at all, it simply
>> ignores its 'end' parameter (and hence also the "all" indicator).
> 
>Sure. the following rfc patch try to fix it. untested since no hardware.

Sure - this needs to be looked at by a person knowing UV (and I would
have thought a change like the one we're discussing here would also
have required an ack from such a person), but ...

>--- a/arch/x86/platform/uv/tlb_uv.c
>+++ b/arch/x86/platform/uv/tlb_uv.c
>@@ -280,12 +280,12 @@ static void bau_process_message(struct msg_desc *mdp, struct bau_control *bcp,
>    /*
>     * This must be a normal message, or retry of a normal message
>     */
>-    if (msg->address == TLB_FLUSH_ALL) {
>+    if (msg->end == 0) {

How would "end" end up being 0 here? Don't you rather mean "start and
end on the same page"? And even if you do, aren't you then losing the
intended optimization?

>+        __flush_tlb_one(msg->start);
>+        stat->d_onetlb++;
>+    } else {
 >        local_flush_tlb();
>        stat->d_alltlb++;
>-    } else {
>-        __flush_tlb_one(msg->address);
>-        stat->d_onetlb++;
>    }
>    stat->d_requestee++;
 >
>@@ -1113,7 +1114,8 @@ const struct cpumask *uv_flush_tlb_others(const struct cpumask *cpumask,
 >
>    record_send_statistics(stat, locals, hubs, remotes, bau_desc);
 >
>-    bau_desc->payload.address = start;
>+    bau_desc->payload.start = start;
>+    bau_desc->payload.end    = end;
>    bau_desc->payload.sending_cpu = cpu;
>    /*
>     * uv_flush_send_and_wait returns 0 if all cpu's were messaged,

Jan

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