Date: Thu, 19 Aug 2010 13:29:25 +0400 From: pluknet <pluknet@gmail.com> To: John Baldwin <jhb@freebsd.org> Cc: Kostik Belousov <kostikbel@gmail.com>, FreeBSD Current <freebsd-current@freebsd.org> Subject: Re: LOR on nfs: vfs_vnops.c:301 kern_descrip.c:1580 Message-ID: <AANLkTikpC9REEQKNUUHtLDxSLB1MmiqKdgbJ0Ee7O%2BGJ@mail.gmail.com> In-Reply-To: <201008181607.52798.jhb@freebsd.org> References: <AANLkTimJ=d06D2z24QyRQ98zEa1Pemk4=vkNGLNiX90N@mail.gmail.com> <AANLkTi=V8bumpGKgi1aLXxhJkdKdpG1jfyrcXbMyc3Yw@mail.gmail.com> <AANLkTikwiTsiZtp5Zej8yDsR2b4%2B=TSL1oD-M_uRFqBd@mail.gmail.com> <201008181607.52798.jhb@freebsd.org>
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[-- Attachment #1 --]
On 19 August 2010 00:07, John Baldwin <jhb@freebsd.org> wrote:
> On Wednesday, August 18, 2010 3:17:56 pm pluknet wrote:
>> On 18 August 2010 23:11, pluknet <pluknet@gmail.com> wrote:
>> > On 18 August 2010 17:46, Kostik Belousov <kostikbel@gmail.com> wrote:
>> >> On Wed, Aug 18, 2010 at 02:43:19PM +0400, pluknet wrote:
>> >>> On 18 August 2010 12:07, pluknet <pluknet@gmail.com> wrote:
>> >>> > On 17 August 2010 20:04, Kostik Belousov <kostikbel@gmail.com> wrote:
>> >>> >
>> >>> >>
>> >>> >> Also please take a note of the John' suggestion to use the taskqueue.
>> >>> >
>> >>> > I decided to go this road. Thank you both.
>> >>> > Now I do nfs buildkernel survive and prepare some benchmark results.
>> >>> >
>> >>>
>> >>> So, I modified the patch to defer proc_create() with taskqueue(9).
>> >>> Below is `time make -j5 buildkernel WITHOUT_MODULES=yes` perf.
> evaluation.
>> >>> Done on 4-way CPU on clean /usr/obj with /usr/src & /usr/obj both
>> >>> nfs-mounted over 1Gbit LAN.
>> >>>
>> >>> clean old
>> >>> 1137.985u 239.411s 7:42.15 298.0% 6538+2133k 87+43388io 226pf+0w
>> >>>
>> >>> clean new
>> >>> 1134.755u 240.032s 7:41.25 298.0% 6553+2133k 87+43367io 224pf+0w
>> >>>
>> >>> Patch needs polishing, though it generally works.
>> >>> Not sure if shep_chan (or whatever name it will get) needs locking.
>> >> As I said yesterday, if several requests to create nfsiod coming one
>> >> after another, you would loose all but the last.
>> >>
>> >> You should put the requests into the list, probably protected by
>> >> nfs_iod_mtx.
>> >>
>> >
>> > How about this patch? Still several things to ask.
>> > 1) I used malloc instance w/ M_NOWAIT, since it's called with nfs_iod_mtx
> held.
>> > 2) Probably busy/done gymnastics is a wrong mess. Your help is
> appreciated.
>> > 3) if (1) is fine, is it right to use fail: logic (i.e. set
>> > NFSIOD_NOT_AVAILABLE)
>> > on memory shortage? Not tested.
>> >
>> > There are debug printf() left intentionally to see how 3 contexts run
> under load
>> > to each other. I attached these messages as well if that makes sense.
>> >
>>
>> Ah, yes. Sorry, forgot about that.
>
> Your task handler needs to run in a loop until the list of requests is empty.
> If multiple threads call taskqueue_enqueue() before your task is scheduled,
> they will be consolidated down to a single call of your task handler.
Thanks for your suggestions.
So I converted nfs_nfsiodnew_tq() into loop, and as such
I changed a cleanup SLIST_FOREACH() as well to free a bulk of
(potentially consolidated) completed requests in one pass.
kproc_create() is still out of the SLIST_FOREACH() to avoid calling it
with nfs_iod_mtx held.
>
> - int error, i;
> - int newiod;
> + int i, newiod, error;
>
> You should sort these alphabetically if you are going to change this. I would
> probably just leave it as-is.
Err.. that's resulted after a set of changes. Thanks for noting that.
>
> Also, I'm not sure how this works as you don't actually wait for the task to
> complete. If the taskqueue_enqueue() doesn't preempt, then you may read
> ni_error as zero before the kproc has actually been created and return success
> even though an nfsiod hasn't been created.
>
I put taskqueue_drain() right after taskqueue_enqueue() to be in sync with
task handler. That was part to think about, as I didn't find such a use pattern.
It seems though that tasks are launched now strictly one-by-one, without
visible parallelism (as far as debug printf()s don't overlap anymore).
--
wbr,
pluknet
[-- Attachment #2 --]
Index: sys/nfsclient/nfs_subs.c
===================================================================
--- sys/nfsclient/nfs_subs.c (revision 211279)
+++ sys/nfsclient/nfs_subs.c (working copy)
@@ -59,6 +59,7 @@
#include <sys/sysent.h>
#include <sys/syscall.h>
#include <sys/sysproto.h>
+#include <sys/taskqueue.h>
#include <vm/vm.h>
#include <vm/vm_object.h>
@@ -117,6 +118,7 @@
struct nfs_bufq nfs_bufq;
static struct mtx nfs_xid_mtx;
+struct task nfs_nfsiodnew_task;
/*
* and the reverse mapping from generic to Version 2 procedure numbers
@@ -354,6 +356,7 @@
*/
mtx_init(&nfs_iod_mtx, "NFS iod lock", NULL, MTX_DEF);
mtx_init(&nfs_xid_mtx, "NFS xid lock", NULL, MTX_DEF);
+ TASK_INIT(&nfs_nfsiodnew_task, 0, nfs_nfsiodnew_tq, NULL);
nfs_pbuf_freecnt = nswbuf / 2 + 1;
Index: sys/nfsclient/nfs_nfsiod.c
===================================================================
--- sys/nfsclient/nfs_nfsiod.c (revision 211279)
+++ sys/nfsclient/nfs_nfsiod.c (working copy)
@@ -59,6 +59,7 @@
#include <sys/fcntl.h>
#include <sys/lockf.h>
#include <sys/mutex.h>
+#include <sys/taskqueue.h>
#include <netinet/in.h>
#include <netinet/tcp.h>
@@ -75,6 +76,17 @@
static void nfssvc_iod(void *);
+struct nfsiod_str {
+ SLIST_ENTRY(nfsiod_str) ni_list;
+ int *ni_inst;
+ int ni_iod;
+ int ni_error;
+ int ni_busy;
+ int ni_done;
+};
+static SLIST_HEAD(, nfsiod_str) nfsiodhead =
+ SLIST_HEAD_INITIALIZER(nfsiodhead);
+
static int nfs_asyncdaemon[NFS_MAXASYNCDAEMON];
SYSCTL_DECL(_vfs_nfs);
@@ -159,11 +171,43 @@
sizeof (nfs_iodmax), sysctl_iodmax, "IU",
"Max number of nfsiod kthreads");
+void
+nfs_nfsiodnew_tq(__unused void *arg, int pending)
+{
+ struct nfsiod_str *nip;
+
+ for (;;) {
+ mtx_lock(&nfs_iod_mtx);
+ SLIST_FOREACH(nip, &nfsiodhead, ni_list) {
+ if (nip->ni_busy == 0) {
+ nip->ni_busy = 1;
+ /*
+ * So we call kproc_create()
+ * after dropping nfs_iod_mtx lock.
+ */
+ break;
+ }
+ }
+ mtx_unlock(&nfs_iod_mtx);
+ /* Complete the task if the list of requests is empty. */
+ if (nip == NULL)
+ break;
+// KASSERT(nip != NULL, ("nfs_nfsiodnew_tq: nip is NULL"));
+ printf("tq: nip: %p\n", nip);
+ printf("tq: ni_inst: %p\n", nip->ni_inst);
+ printf("tq: ni_iod: %d\n", nip->ni_iod);
+ nip->ni_error = kproc_create(nfssvc_iod, nip->ni_inst, NULL,
+ RFHIGHPID, 0, "nfsiod %d", nip->ni_iod);
+ nip->ni_done = 1;
+ }
+}
+
int
nfs_nfsiodnew(int set_iodwant)
{
int error, i;
int newiod;
+ struct nfsiod_str *nip, *nip_temp;
if (nfs_numasync >= nfs_iodmax)
return (-1);
@@ -178,17 +222,35 @@
return (-1);
if (set_iodwant > 0)
nfs_iodwant[i] = NFSIOD_CREATED_FOR_NFS_ASYNCIO;
+ nip = malloc(sizeof(*nip), M_TEMP, M_NOWAIT | M_ZERO);
+ if (nip == NULL)
+ goto fail;
+ nip->ni_inst = nfs_asyncdaemon + i;
+ nip->ni_iod = newiod;
+ SLIST_INSERT_HEAD(&nfsiodhead, nip, ni_list);
mtx_unlock(&nfs_iod_mtx);
- error = kproc_create(nfssvc_iod, nfs_asyncdaemon + i, NULL, RFHIGHPID,
- 0, "nfsiod %d", newiod);
+ printf("new: nip: %p\n", nip);
+ printf("new: ni_inst: %p\n", nip->ni_inst);
+ printf("new: ni_iod: %d\n", nip->ni_iod);
+ taskqueue_enqueue(taskqueue_thread, &nfs_nfsiodnew_task);
+ taskqueue_drain(taskqueue_thread, &nfs_nfsiodnew_task);
mtx_lock(&nfs_iod_mtx);
- if (error) {
- if (set_iodwant > 0)
- nfs_iodwant[i] = NFSIOD_NOT_AVAILABLE;
- return (-1);
+ error = nip->ni_error;
+ SLIST_FOREACH_SAFE(nip, &nfsiodhead, ni_list, nip_temp) {
+ if (nip->ni_busy != 0 && nip->ni_done != 0) {
+ SLIST_REMOVE(&nfsiodhead, nip, nfsiod_str, ni_list);
+ free(nip, M_TEMP);
+// break;
+ }
}
+ if (error)
+ goto fail;
nfs_numasync++;
return (newiod);
+fail:
+ if (set_iodwant > 0)
+ nfs_iodwant[i] = NFSIOD_NOT_AVAILABLE;
+ return (-1);
}
static void
@@ -231,6 +293,8 @@
mtx_lock(&nfs_iod_mtx);
myiod = (int *)instance - nfs_asyncdaemon;
+ printf("instance: %p\n", instance);
+ printf("myiod: %d\n", myiod);
/*
* Main loop
*/
Index: sys/nfsclient/nfs.h
===================================================================
--- sys/nfsclient/nfs.h (revision 211279)
+++ sys/nfsclient/nfs.h (working copy)
@@ -125,6 +125,7 @@
extern struct nfsstats nfsstats;
extern struct mtx nfs_iod_mtx;
+extern struct task nfs_nfsiodnew_task;
extern int nfs_numasync;
extern unsigned int nfs_iodmax;
@@ -253,6 +254,7 @@
struct ucred *cred, struct thread *td);
int nfs_readdirrpc(struct vnode *, struct uio *, struct ucred *);
int nfs_nfsiodnew(int);
+void nfs_nfsiodnew_tq(__unused void *, int);
int nfs_asyncio(struct nfsmount *, struct buf *, struct ucred *, struct thread *);
int nfs_doio(struct vnode *, struct buf *, struct ucred *, struct thread *);
void nfs_doio_directwrite (struct buf *);
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