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Message-ID: <alpine.LNX.2.00.1011211941240.19813@swampdragon.chaosbits.net>
Date: Sun, 21 Nov 2010 19:48:41 +0100 (CET)
From: Jesper Juhl <jj@...osbits.net>
To: Linus Torvalds <torvalds@...ux-foundation.org>
cc: linux-scsi@...r.kernel.org,
"James E.J. Bottomley" <James.Bottomley@...e.de>,
linux-kernel@...r.kernel.org, Eric Youngdale <eric@...ante.org>,
"David S. Miller" <davem@...emloft.net>,
Mike Anderson <andmike@...ibm.com>,
Russell King <rmk@....linux.org.uk>,
Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH][resend][SCSI] Reduce number of sequential pointer derefs
in scsi_error.c and reduce size as well
On Sat, 20 Nov 2010, Linus Torvalds wrote:
> On Sat, Nov 20, 2010 at 12:30 PM, Jesper Juhl <jj@...osbits.net> wrote:
> >
> > Ok, I tried doing that (see patch below)
>
> Actually, you kind of chose exactly the reverse of the functions I'd
> have chosen.
>
> Try doing the added parameter to the small static helper functions.
> Those are the ones that tend to get inlined, and then the parameter
> should actually result in _fewer_ pointer reloads.
>
> So the ones like this:
>
> > static int __scsi_try_to_abort_cmd(struct scsi_cmnd *scmd)
[...]
I see your point now.
I tried this with most of the functions where it seemed that it could
possibly be a gain, but in the end it turned out that only the one you
pointed out above actually saw any benefit, so that's the only one I
changed.
In the end, the object size is down to this:
text data bss dec hex filename
18713 128 4704 23545 5bf9 drivers/scsi/scsi_error.o
from this:
text data bss dec hex filename
18790 128 4712 23630 5c4e drivers/scsi/scsi_error.o
and the patch looks like this now:
Signed-off-by: Jesper Juhl <jj@...osbits.net>
---
scsi_error.c | 93 +++++++++++++++++++++++++++++++----------------------------
1 file changed, 49 insertions(+), 44 deletions(-)
diff --git a/drivers/scsi/scsi_error.c b/drivers/scsi/scsi_error.c
index 824b8fc..1d7958a 100644
--- a/drivers/scsi/scsi_error.c
+++ b/drivers/scsi/scsi_error.c
@@ -3,14 +3,14 @@
*
* SCSI error/timeout handling
* Initial versions: Eric Youngdale. Based upon conversations with
- * Leonard Zubkoff and David Miller at Linux Expo,
+ * Leonard Zubkoff and David Miller at Linux Expo,
* ideas originating from all over the place.
*
* Restructured scsi_unjam_host and associated functions.
* September 04, 2002 Mike Anderson (andmike@...ibm.com)
*
* Forward port of Russell King's (rmk@....linux.org.uk) changes and
- * minor cleanups.
+ * minor cleanups.
* September 30, 2002 Mike Anderson (andmike@...ibm.com)
*/
@@ -129,14 +129,15 @@ enum blk_eh_timer_return scsi_times_out(struct request *req)
{
struct scsi_cmnd *scmd = req->special;
enum blk_eh_timer_return rtn = BLK_EH_NOT_HANDLED;
+ struct Scsi_Host *host = scmd->device->host;
trace_scsi_dispatch_cmd_timeout(scmd);
scsi_log_completion(scmd, TIMEOUT_ERROR);
- if (scmd->device->host->transportt->eh_timed_out)
- rtn = scmd->device->host->transportt->eh_timed_out(scmd);
- else if (scmd->device->host->hostt->eh_timed_out)
- rtn = scmd->device->host->hostt->eh_timed_out(scmd);
+ if (host->transportt->eh_timed_out)
+ rtn = host->transportt->eh_timed_out(scmd);
+ else if (host->hostt->eh_timed_out)
+ rtn = host->hostt->eh_timed_out(scmd);
if (unlikely(rtn == BLK_EH_NOT_HANDLED &&
!scsi_eh_scmd_add(scmd, SCSI_EH_CANCEL_CMD))) {
@@ -195,7 +196,7 @@ static inline void scsi_eh_prt_fail_stats(struct Scsi_Host *shost,
++total_failures;
if (scmd->eh_eflags & SCSI_EH_CANCEL_CMD)
++cmd_cancel;
- else
+ else
++cmd_failed;
}
}
@@ -294,7 +295,7 @@ static int scsi_check_sense(struct scsi_cmnd *scmd)
return NEEDS_RETRY;
}
/*
- * if the device is in the process of becoming ready, we
+ * if the device is in the process of becoming ready, we
* should retry.
*/
if ((sshdr.asc == 0x04) && (sshdr.ascq == 0x01))
@@ -488,7 +489,7 @@ static int scsi_eh_completed_normally(struct scsi_cmnd *scmd)
*/
static void scsi_eh_done(struct scsi_cmnd *scmd)
{
- struct completion *eh_action;
+ struct completion *eh_action;
SCSI_LOG_ERROR_RECOVERY(3,
printk("%s scmd: %p result: %x\n",
@@ -507,22 +508,23 @@ static int scsi_try_host_reset(struct scsi_cmnd *scmd)
{
unsigned long flags;
int rtn;
+ struct Scsi_Host *host = scmd->device->host;
+ struct scsi_host_template *hostt = host->hostt;
SCSI_LOG_ERROR_RECOVERY(3, printk("%s: Snd Host RST\n",
__func__));
- if (!scmd->device->host->hostt->eh_host_reset_handler)
+ if (!hostt->eh_host_reset_handler)
return FAILED;
- rtn = scmd->device->host->hostt->eh_host_reset_handler(scmd);
+ rtn = hostt->eh_host_reset_handler(scmd);
if (rtn == SUCCESS) {
- if (!scmd->device->host->hostt->skip_settle_delay)
+ if (!hostt->skip_settle_delay)
ssleep(HOST_RESET_SETTLE_TIME);
- spin_lock_irqsave(scmd->device->host->host_lock, flags);
- scsi_report_bus_reset(scmd->device->host,
- scmd_channel(scmd));
- spin_unlock_irqrestore(scmd->device->host->host_lock, flags);
+ spin_lock_irqsave(host->host_lock, flags);
+ scsi_report_bus_reset(host, scmd_channel(scmd));
+ spin_unlock_irqrestore(host->host_lock, flags);
}
return rtn;
@@ -536,22 +538,23 @@ static int scsi_try_bus_reset(struct scsi_cmnd *scmd)
{
unsigned long flags;
int rtn;
+ struct Scsi_Host *host = scmd->device->host;
+ struct scsi_host_template *hostt = host->hostt;
SCSI_LOG_ERROR_RECOVERY(3, printk("%s: Snd Bus RST\n",
__func__));
- if (!scmd->device->host->hostt->eh_bus_reset_handler)
+ if (!hostt->eh_bus_reset_handler)
return FAILED;
- rtn = scmd->device->host->hostt->eh_bus_reset_handler(scmd);
+ rtn = hostt->eh_bus_reset_handler(scmd);
if (rtn == SUCCESS) {
- if (!scmd->device->host->hostt->skip_settle_delay)
+ if (!hostt->skip_settle_delay)
ssleep(BUS_RESET_SETTLE_TIME);
- spin_lock_irqsave(scmd->device->host->host_lock, flags);
- scsi_report_bus_reset(scmd->device->host,
- scmd_channel(scmd));
- spin_unlock_irqrestore(scmd->device->host->host_lock, flags);
+ spin_lock_irqsave(host->host_lock, flags);
+ scsi_report_bus_reset(host, scmd_channel(scmd));
+ spin_unlock_irqrestore(host->host_lock, flags);
}
return rtn;
@@ -577,16 +580,18 @@ static int scsi_try_target_reset(struct scsi_cmnd *scmd)
{
unsigned long flags;
int rtn;
+ struct Scsi_Host *host = scmd->device->host;
+ struct scsi_host_template *hostt = host->hostt;
- if (!scmd->device->host->hostt->eh_target_reset_handler)
+ if (!hostt->eh_target_reset_handler)
return FAILED;
- rtn = scmd->device->host->hostt->eh_target_reset_handler(scmd);
+ rtn = hostt->eh_target_reset_handler(scmd);
if (rtn == SUCCESS) {
- spin_lock_irqsave(scmd->device->host->host_lock, flags);
+ spin_lock_irqsave(host->host_lock, flags);
__starget_for_each_device(scsi_target(scmd->device), NULL,
__scsi_report_device_reset);
- spin_unlock_irqrestore(scmd->device->host->host_lock, flags);
+ spin_unlock_irqrestore(host->host_lock, flags);
}
return rtn;
@@ -605,22 +610,23 @@ static int scsi_try_target_reset(struct scsi_cmnd *scmd)
static int scsi_try_bus_device_reset(struct scsi_cmnd *scmd)
{
int rtn;
+ struct scsi_host_template *hostt = scmd->device->host->hostt;
- if (!scmd->device->host->hostt->eh_device_reset_handler)
+ if (!hostt->eh_device_reset_handler)
return FAILED;
- rtn = scmd->device->host->hostt->eh_device_reset_handler(scmd);
+ rtn = hostt->eh_device_reset_handler(scmd);
if (rtn == SUCCESS)
__scsi_report_device_reset(scmd->device, NULL);
return rtn;
}
-static int __scsi_try_to_abort_cmd(struct scsi_cmnd *scmd)
+static int __scsi_try_to_abort_cmd(struct scsi_host_template *hostt,
+ struct scsi_cmnd *scmd)
{
- if (!scmd->device->host->hostt->eh_abort_handler)
+ if (!hostt->eh_abort_handler)
return FAILED;
-
- return scmd->device->host->hostt->eh_abort_handler(scmd);
+ return hostt->eh_abort_handler(scmd);
}
/**
@@ -642,12 +648,12 @@ static int scsi_try_to_abort_cmd(struct scsi_cmnd *scmd)
*/
if (scmd->serial_number == 0)
return SUCCESS;
- return __scsi_try_to_abort_cmd(scmd);
+ return __scsi_try_to_abort_cmd(scmd->device->host->hostt, scmd);
}
static void scsi_abort_eh_cmnd(struct scsi_cmnd *scmd)
{
- if (__scsi_try_to_abort_cmd(scmd) != SUCCESS)
+ if (__scsi_try_to_abort_cmd(scmd->device->host->hostt, scmd) != SUCCESS)
if (scsi_try_bus_device_reset(scmd) != SUCCESS)
if (scsi_try_target_reset(scmd) != SUCCESS)
if (scsi_try_bus_reset(scmd) != SUCCESS)
@@ -867,7 +873,7 @@ EXPORT_SYMBOL(scsi_eh_finish_cmd);
*
* Description:
* See if we need to request sense information. if so, then get it
- * now, so we have a better idea of what to do.
+ * now, so we have a better idea of what to do.
*
* Notes:
* This has the unfortunate side effect that if a shost adapter does
@@ -987,7 +993,6 @@ static int scsi_eh_abort_cmds(struct list_head *work_q,
!scsi_eh_tur(scmd)) {
scsi_eh_finish_cmd(scmd, done_q);
}
-
} else
SCSI_LOG_ERROR_RECOVERY(3, printk("%s: aborting"
" cmd failed:"
@@ -1031,7 +1036,7 @@ static int scsi_eh_try_stu(struct scsi_cmnd *scmd)
*
* Notes:
* If commands are failing due to not ready, initializing command required,
- * try revalidating the device, which will end up sending a start unit.
+ * try revalidating the device, which will end up sending a start unit.
*/
static int scsi_eh_stu(struct Scsi_Host *shost,
struct list_head *work_q,
@@ -1085,7 +1090,7 @@ static int scsi_eh_stu(struct Scsi_Host *shost,
* Try a bus device reset. Still, look to see whether we have multiple
* devices that are jammed or not - if we have multiple devices, it
* makes no sense to try bus_device_reset - we really would need to try
- * a bus_reset instead.
+ * a bus_reset instead.
*/
static int scsi_eh_bus_device_reset(struct Scsi_Host *shost,
struct list_head *work_q,
@@ -1196,7 +1201,7 @@ static int scsi_eh_target_reset(struct Scsi_Host *shost,
}
/**
- * scsi_eh_bus_reset - send a bus reset
+ * scsi_eh_bus_reset - send a bus reset
* @shost: &scsi host being recovered.
* @work_q: &list_head for pending commands.
* @done_q: &list_head for processed commands.
@@ -1213,7 +1218,7 @@ static int scsi_eh_bus_reset(struct Scsi_Host *shost,
* we really want to loop over the various channels, and do this on
* a channel by channel basis. we should also check to see if any
* of the failed commands are on soft_reset devices, and if so, skip
- * the reset.
+ * the reset.
*/
for (channel = 0; channel <= shost->max_channel; channel++) {
@@ -1255,7 +1260,7 @@ static int scsi_eh_bus_reset(struct Scsi_Host *shost,
}
/**
- * scsi_eh_host_reset - send a host reset
+ * scsi_eh_host_reset - send a host reset
* @work_q: list_head for processed commands.
* @done_q: list_head for processed commands.
*/
@@ -1408,7 +1413,7 @@ int scsi_decide_disposition(struct scsi_cmnd *scmd)
return SUCCESS;
/*
* when the low level driver returns did_soft_error,
- * it is responsible for keeping an internal retry counter
+ * it is responsible for keeping an internal retry counter
* in order to avoid endless loops (db)
*
* actually this is a bug in this function here. we should
@@ -2005,7 +2010,7 @@ int scsi_normalize_sense(const u8 *sense_buffer, int sb_len,
if (sb_len > 7)
sshdr->additional_length = sense_buffer[7];
} else {
- /*
+ /*
* fixed format
*/
if (sb_len > 2)
--
Jesper Juhl <jj@...osbits.net> http://www.chaosbits.net/
Don't top-post http://www.catb.org/~esr/jargon/html/T/top-post.html
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