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    SubjectRe: Increase page fault rate by prezeroing V1 [3/3]: Altix SN2 BTE Zeroing
    We still need to talk.  This is a much smaller patch, which I like.  The
    problem I see in my 30 second review is you are doing things per-cpu
    when they really need to be done per-node. It is very likely that
    there will be M-Bricks in the system (cranberry2 has one if you want
    to test your code out there or you can take any altix and disable the
    cpus on a C-Brick). With M-Bricks, you will essentially limit
    yourself to one zero operation per controlling node instead of one
    per node.

    I think the easy answer is to not have the structure allocated
    within bte_copy(), but rather within bte_start_zero and passed
    in as the notification address.

    Give me a call sometime today (Wed. I am in the office from about
    10:00 CDT until around 4:00 CDT) Maybe we can get this straightened
    out quickly. If you are not calling from the office, email me with
    other arrangements.

    Thanks,
    Robin

    On Tue, Dec 21, 2004 at 11:57:57AM -0800, Christoph Lameter wrote:
    > o Use the Block Transfer Engine in the Altix SN2 SHub for background zeroing
    >
    > Index: linux-2.6.9/arch/ia64/sn/kernel/bte.c
    > ===================================================================
    > --- linux-2.6.9.orig/arch/ia64/sn/kernel/bte.c 2004-12-17 14:40:10.000000000 -0800
    > +++ linux-2.6.9/arch/ia64/sn/kernel/bte.c 2004-12-21 11:03:49.000000000 -0800
    > @@ -4,6 +4,8 @@
    > * for more details.
    > *
    > * Copyright (c) 2000-2003 Silicon Graphics, Inc. All Rights Reserved.
    > + *
    > + * Support for zeroing pages, Christoph Lameter, SGI, December 2004.
    > */
    >
    > #include <linux/config.h>
    > @@ -20,6 +22,8 @@
    > #include <linux/bootmem.h>
    > #include <linux/string.h>
    > #include <linux/sched.h>
    > +#include <linux/mm.h>
    > +#include <linux/scrub.h>
    >
    > #include <asm/sn/bte.h>
    >
    > @@ -30,7 +34,11 @@
    > /* two interfaces on two btes */
    > #define MAX_INTERFACES_TO_TRY 4
    >
    > -static struct bteinfo_s *bte_if_on_node(nasid_t nasid, int interface)
    > +DEFINE_PER_CPU(u64 *, bte_zero_notify);
    > +
    > +#define bte_zero_notify __get_cpu_var(bte_zero_notify)
    > +
    > +static inline struct bteinfo_s *bte_if_on_node(nasid_t nasid, int interface)
    > {
    > nodepda_t *tmp_nodepda;
    >
    > @@ -132,7 +140,6 @@
    > if (bte == NULL) {
    > continue;
    > }
    > -
    > if (spin_trylock(&bte->spinlock)) {
    > if (!(*bte->most_rcnt_na & BTE_WORD_AVAILABLE) ||
    > (BTE_LNSTAT_LOAD(bte) & BTE_ACTIVE)) {
    > @@ -157,7 +164,7 @@
    > }
    > } while (1);
    >
    > - if (notification == NULL) {
    > + if (notification == NULL || (mode & BTE_NOTIFY_AND_GET_POINTER)) {
    > /* User does not want to be notified. */
    > bte->most_rcnt_na = &bte->notify;
    > } else {
    > @@ -192,6 +199,8 @@
    >
    > itc_end = ia64_get_itc() + (40000000 * local_cpu_data->cyc_per_usec);
    >
    > + if (mode & BTE_NOTIFY_AND_GET_POINTER)
    > + *(u64 volatile **)(notification) = &bte->notify;
    > spin_unlock_irqrestore(&bte->spinlock, irq_flags);
    >
    > if (notification != NULL) {
    > @@ -449,5 +458,31 @@
    > mynodepda->bte_if[i].cleanup_active = 0;
    > mynodepda->bte_if[i].bh_error = 0;
    > }
    > +}
    > +
    > +static int bte_check_bzero(void)
    > +{
    > + return *bte_zero_notify != BTE_WORD_BUSY;
    > +}
    > +
    > +static int bte_start_bzero(void *p, unsigned long len)
    > +{
    > + /* Check limitations.
    > + 1. System must be running (weird things happen during bootup)
    > + 2. Size >64KB. Smaller requests cause too much bte traffic
    > + */
    > + if (len >= BTE_MAX_XFER || len < 60000 || system_state != SYSTEM_RUNNING)
    > + return EINVAL;
    > +
    > + return bte_zero(ia64_tpa(p), len, BTE_NOTIFY_AND_GET_POINTER, &bte_zero_notify);
    > +}
    > +
    > +static struct zero_driver bte_bzero = {
    > + .start = bte_start_bzero,
    > + .check = bte_check_bzero,
    > + .rate = 500000000 /* 500 MB /sec */
    > +};
    >
    > +void sn_bte_bzero_init(void) {
    > + register_zero_driver(&bte_bzero);
    > }
    > Index: linux-2.6.9/arch/ia64/sn/kernel/setup.c
    > ===================================================================
    > --- linux-2.6.9.orig/arch/ia64/sn/kernel/setup.c 2004-12-17 14:40:10.000000000 -0800
    > +++ linux-2.6.9/arch/ia64/sn/kernel/setup.c 2004-12-21 11:02:35.000000000 -0800
    > @@ -243,6 +243,7 @@
    > int pxm;
    > int major = sn_sal_rev_major(), minor = sn_sal_rev_minor();
    > extern void sn_cpu_init(void);
    > + extern void sn_bte_bzero_init(void);
    >
    > /*
    > * If the generic code has enabled vga console support - lets
    > @@ -333,6 +334,7 @@
    > screen_info = sn_screen_info;
    >
    > sn_timer_init();
    > + sn_bte_bzero_init();
    > }
    >
    > /**
    > Index: linux-2.6.9/include/asm-ia64/sn/bte.h
    > ===================================================================
    > --- linux-2.6.9.orig/include/asm-ia64/sn/bte.h 2004-12-17 14:40:16.000000000 -0800
    > +++ linux-2.6.9/include/asm-ia64/sn/bte.h 2004-12-21 11:02:35.000000000 -0800
    > @@ -48,6 +48,8 @@
    > #define BTE_ZERO_FILL (BTE_NOTIFY | IBCT_ZFIL_MODE)
    > /* Use a reserved bit to let the caller specify a wait for any BTE */
    > #define BTE_WACQUIRE (0x4000)
    > +/* Return the pointer to the notification cacheline to the user */
    > +#define BTE_NOTIFY_AND_GET_POINTER (0x8000)
    > /* Use the BTE on the node with the destination memory */
    > #define BTE_USE_DEST (BTE_WACQUIRE << 1)
    > /* Use any available BTE interface on any node for the transfer */
    -
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