From: Benjamin Herrenschmidt <benh@kernel.crashing.org> To: Eric Van Hensbergen <ericvh@gmail.com> Cc: linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, bg-linux@lists.anl-external.org Subject: Re: [PATCH 6/7] [RFC] enable early TLBs for BG/P Date: Fri, 20 May 2011 11:54:02 +1000 [thread overview] Message-ID: <1305856442.7481.120.camel@pasglop> (raw) In-Reply-To: <BANLkTinAqeu7C+U_HFrOAOctFTuSUwG-iA@mail.gmail.com> On Thu, 2011-05-19 at 20:21 -0500, Eric Van Hensbergen wrote: > On Thu, May 19, 2011 at 7:39 PM, Benjamin Herrenschmidt > <benh@kernel.crashing.org> wrote: > > On Wed, 2011-05-18 at 16:24 -0500, Eric Van Hensbergen wrote: > >> BG/P maps firmware with an early TLB > > > > That's a bit gross. How often do you call that firmware in practice ? > > Aren't you better off instead inserting a TLB entry for it when you call > > it instead ? A simple tlbsx. + tlbwe sequence would do. That would free > > up a TLB entry for normal use. > > > > Well, it depends on who you talk to. The production software BG/P > guys use the firmware constantly, its the primary interface to the networks, the console, > and the management software which runs the machine. Yuck. > As such the IO Node guys, the Compute Node Kernel guys and the > ZeptoOS guys use it quite a bit. The kittyhawk guys on the other hand > barely use it at all, in fact I believe they do all the interaction with > it during uboot and then shut it off. I would prefer that approach. > IIRC, the sticky question is RAS support, there are certain things it > wants to jump to firmware to deal with and expects things to be mapped > an pinned into memory. > > Furthermore, I think it may make assumptions about where in the TLB the > mappings are. This is gross, especially on a system with only 64 SW loaded TLB entries :-( > Since the kittyhawk guys > obviously ignore this by shutting it down, its not clear just how > important this is. I'm game to > try the dynamic mapping as you suggest if you would prefer it. I would yes, we can sort things out later for RAS. > Its worth mentioning that I believe with BG/Q, the plan is to rely on > the firmware even more extensively, but I haven't looked at any of the code yet to verify > whether or not this is true. This is tantamount to linking a binary blob with the kernel ... it's a fine line. At some point we might refuse the patches if they go too far in that direction. Cheers, Ben. > -eric > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/
WARNING: multiple messages have this Message-ID (diff)
From: Benjamin Herrenschmidt <benh@kernel.crashing.org> To: Eric Van Hensbergen <ericvh@gmail.com> Cc: linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, bg-linux@lists.anl-external.org Subject: Re: [PATCH 6/7] [RFC] enable early TLBs for BG/P Date: Fri, 20 May 2011 11:54:02 +1000 [thread overview] Message-ID: <1305856442.7481.120.camel@pasglop> (raw) In-Reply-To: <BANLkTinAqeu7C+U_HFrOAOctFTuSUwG-iA@mail.gmail.com> On Thu, 2011-05-19 at 20:21 -0500, Eric Van Hensbergen wrote: > On Thu, May 19, 2011 at 7:39 PM, Benjamin Herrenschmidt > <benh@kernel.crashing.org> wrote: > > On Wed, 2011-05-18 at 16:24 -0500, Eric Van Hensbergen wrote: > >> BG/P maps firmware with an early TLB > > > > That's a bit gross. How often do you call that firmware in practice ? > > Aren't you better off instead inserting a TLB entry for it when you call > > it instead ? A simple tlbsx. + tlbwe sequence would do. That would free > > up a TLB entry for normal use. > > > > Well, it depends on who you talk to. The production software BG/P > guys use the firmware constantly, its the primary interface to the networks, the console, > and the management software which runs the machine. Yuck. > As such the IO Node guys, the Compute Node Kernel guys and the > ZeptoOS guys use it quite a bit. The kittyhawk guys on the other hand > barely use it at all, in fact I believe they do all the interaction with > it during uboot and then shut it off. I would prefer that approach. > IIRC, the sticky question is RAS support, there are certain things it > wants to jump to firmware to deal with and expects things to be mapped > an pinned into memory. > > Furthermore, I think it may make assumptions about where in the TLB the > mappings are. This is gross, especially on a system with only 64 SW loaded TLB entries :-( > Since the kittyhawk guys > obviously ignore this by shutting it down, its not clear just how > important this is. I'm game to > try the dynamic mapping as you suggest if you would prefer it. I would yes, we can sort things out later for RAS. > Its worth mentioning that I believe with BG/Q, the plan is to rely on > the firmware even more extensively, but I haven't looked at any of the code yet to verify > whether or not this is true. This is tantamount to linking a binary blob with the kernel ... it's a fine line. At some point we might refuse the patches if they go too far in that direction. Cheers, Ben. > -eric > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/
next prev parent reply other threads:[~2011-05-20 1:54 UTC|newest] Thread overview: 79+ messages / expand[flat|nested] mbox.gz Atom feed top 2011-05-18 21:24 [PATCH 1/7] [RFC] Mainline BG/P platform support Eric Van Hensbergen 2011-05-18 21:24 ` Eric Van Hensbergen 2011-05-18 21:24 ` [PATCH 2/7] [RFC] add bluegene entry to cputable Eric Van Hensbergen 2011-05-18 21:24 ` Eric Van Hensbergen 2011-05-20 0:35 ` Benjamin Herrenschmidt 2011-05-20 0:35 ` Benjamin Herrenschmidt 2011-05-20 1:08 ` Eric Van Hensbergen 2011-05-20 1:08 ` Eric Van Hensbergen 2011-05-20 1:50 ` Benjamin Herrenschmidt 2011-05-20 1:50 ` Benjamin Herrenschmidt 2011-05-18 21:24 ` [PATCH 3/7] [RFC] add support for BlueGene/P FPU Eric Van Hensbergen 2011-05-18 21:24 ` Eric Van Hensbergen 2011-05-19 5:58 ` Michael Neuling 2011-05-19 5:58 ` Michael Neuling 2011-05-19 13:53 ` Eric Van Hensbergen 2011-05-19 13:53 ` Eric Van Hensbergen 2011-05-19 15:22 ` [bg-linux] " Kazutomo Yoshii 2011-05-19 21:36 ` Michael Neuling 2011-05-19 21:36 ` Michael Neuling 2011-05-19 21:55 ` Eric Van Hensbergen 2011-05-19 21:55 ` Eric Van Hensbergen 2011-05-19 23:16 ` Michael Neuling 2011-05-19 23:16 ` Michael Neuling 2011-05-20 0:30 ` Eric Van Hensbergen 2011-05-20 0:30 ` Eric Van Hensbergen 2011-05-20 0:43 ` Michael Neuling 2011-05-20 0:43 ` Michael Neuling 2011-05-20 0:53 ` Benjamin Herrenschmidt 2011-05-20 0:52 ` Benjamin Herrenschmidt 2011-05-20 0:52 ` Benjamin Herrenschmidt 2011-05-19 21:41 ` [PATCH 3/7] [RFC][V2] add support for BlueGene/P Double FPU Eric Van Hensbergen 2011-05-19 21:41 ` Eric Van Hensbergen 2011-05-18 21:24 ` [PATCH 4/7] [RFC] enable L1_WRITETHROUGH mode for BG/P Eric Van Hensbergen 2011-05-18 21:24 ` Eric Van Hensbergen 2011-05-19 10:43 ` Josh Boyer 2011-05-19 10:43 ` Josh Boyer 2011-05-19 12:53 ` Eric Van Hensbergen 2011-05-19 12:53 ` Eric Van Hensbergen 2011-05-19 21:42 ` [PATCH 4/7] [RFC][V2] enable BGP_L1_WRITETHROUGH " Eric Van Hensbergen 2011-05-19 21:42 ` Eric Van Hensbergen 2011-05-20 1:01 ` [PATCH 4/7] [RFC] enable L1_WRITETHROUGH " Benjamin Herrenschmidt 2011-05-20 1:01 ` Benjamin Herrenschmidt 2011-05-18 21:24 ` [PATCH 5/7] [RFC] force 32-byte aligned kmallocs Eric Van Hensbergen 2011-05-18 21:24 ` Eric Van Hensbergen 2011-05-20 0:36 ` Benjamin Herrenschmidt 2011-05-20 0:36 ` Benjamin Herrenschmidt 2011-05-20 0:47 ` Eric Van Hensbergen 2011-05-20 0:47 ` Eric Van Hensbergen 2011-05-20 1:50 ` Benjamin Herrenschmidt 2011-05-20 1:50 ` Benjamin Herrenschmidt 2011-05-20 1:32 ` [bg-linux] " Kazutomo Yoshii 2011-05-20 2:08 ` Benjamin Herrenschmidt 2011-05-20 2:08 ` Benjamin Herrenschmidt 2011-05-20 2:13 ` Benjamin Herrenschmidt 2011-05-20 2:13 ` Benjamin Herrenschmidt 2011-05-20 3:02 ` Kazutomo Yoshii 2011-05-20 3:13 ` Benjamin Herrenschmidt 2011-05-18 21:24 ` [PATCH 6/7] [RFC] enable early TLBs for BG/P Eric Van Hensbergen 2011-05-18 21:24 ` Eric Van Hensbergen 2011-05-20 0:39 ` Benjamin Herrenschmidt 2011-05-20 0:39 ` Benjamin Herrenschmidt 2011-05-20 1:21 ` Eric Van Hensbergen 2011-05-20 1:21 ` Eric Van Hensbergen 2011-05-20 1:54 ` Benjamin Herrenschmidt [this message] 2011-05-20 1:54 ` Benjamin Herrenschmidt 2011-05-20 3:38 ` [bg-linux] " Kazutomo Yoshii 2011-05-20 3:38 ` Kazutomo Yoshii 2011-05-20 3:52 ` Benjamin Herrenschmidt 2011-05-20 3:52 ` Benjamin Herrenschmidt 2011-05-20 13:01 ` Eric Van Hensbergen 2011-05-20 22:20 ` Benjamin Herrenschmidt 2011-05-18 21:24 ` [PATCH 7/7] [RFC] SMP support code Eric Van Hensbergen 2011-05-18 21:24 ` Eric Van Hensbergen 2011-05-20 1:05 ` Benjamin Herrenschmidt 2011-05-20 1:05 ` Benjamin Herrenschmidt 2011-05-19 11:01 ` [PATCH 1/7] [RFC] Mainline BG/P platform support Josh Boyer 2011-05-19 11:01 ` Josh Boyer 2011-05-19 12:35 ` Eric Van Hensbergen 2011-05-19 12:35 ` Eric Van Hensbergen
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