Messages in this thread Patch in this message | | | Date | Thu, 27 Jul 2017 08:31:28 +0200 | From | Jean Delvare <> | Subject | [PATCH] firmware: dmi: Optimize dmi_matches |
| |
Function dmi_matches can me made a bit faster:
* The documented purpose of dmi_initialized is to catch too early calls to dmi_check_system(). I'm not fully convinced it justifies slowing down the initialization of all systems out there, but at least the check should not have been moved from dmi_check_system() to dmi_matches(). dmi_matches() is being called for every entry of the table passed to dmi_check_system(), causing the same redundant check to be performed again and again. So move it back to dmi_check_system(), reverting this specific portion of commit d7b1956fed33 ("DMI: Introduce dmi_first_match to make the interface more flexible").
* Don't check for the exact_match flag again when we already know its value.
Signed-off-by: Jean Delvare <jdelvare@suse.de> Cc: Jani Nikula <jani.nikula@linux.intel.com> Cc: Daniel Vetter <daniel.vetter@intel.com> Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com> Cc: Jeff Garzik <jgarzik@redhat.com> --- Regarding dmi_initialized, I don't think it makes sense to check for a possible bad initialization order at run time on every system when it is all decided at build time. If a developer introduces a new call to dmi_check_system() and it is too early in the initialization sequence, I believe he/she would notice upon first testing, and a comment to his/her intention in the source code would serve the same purpose without the worldwide performance penalty. Would anyone object to such a change?
drivers/firmware/dmi_scan.c | 19 +++++++++++-------- 1 file changed, 11 insertions(+), 8 deletions(-)
--- linux-4.12.orig/drivers/firmware/dmi_scan.c 2017-07-27 08:15:38.283519194 +0200 +++ linux-4.12/drivers/firmware/dmi_scan.c 2017-07-27 08:26:23.013053058 +0200 @@ -784,19 +784,20 @@ static bool dmi_matches(const struct dmi { int i; - WARN(!dmi_initialized, KERN_ERR "dmi check: not initialized yet.\n"); - for (i = 0; i < ARRAY_SIZE(dmi->matches); i++) { int s = dmi->matches[i].slot; if (s == DMI_NONE) break; if (dmi_ident[s]) { - if (!dmi->matches[i].exact_match && - strstr(dmi_ident[s], dmi->matches[i].substr)) - continue; - else if (dmi->matches[i].exact_match && - !strcmp(dmi_ident[s], dmi->matches[i].substr)) - continue; + if (dmi->matches[i].exact_match) { + if (!strcmp(dmi_ident[s], + dmi->matches[i].substr)) + continue; + } else { + if (strstr(dmi_ident[s], + dmi->matches[i].substr)) + continue; + } } /* No match */ @@ -832,6 +833,8 @@ int dmi_check_system(const struct dmi_sy int count = 0; const struct dmi_system_id *d; + WARN(!dmi_initialized, KERN_ERR "dmi check: not initialized yet.\n"); + for (d = list; !dmi_is_end_of_table(d); d++) if (dmi_matches(d)) { count++; -- Jean Delvare SUSE L3 Support
| |