Message ID | 20231118155105.25678-25-yury.norov@gmail.com |
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State | New |
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Sat, 18 Nov 2023 07:51:44 -0800 (PST) From: Yury Norov <yury.norov@gmail.com> To: linux-kernel@vger.kernel.org, Karsten Keil <isdn@linux-pingi.de>, netdev@vger.kernel.org Cc: Yury Norov <yury.norov@gmail.com>, Jan Kara <jack@suse.cz>, Mirsad Todorovac <mirsad.todorovac@alu.unizg.hr>, Matthew Wilcox <willy@infradead.org>, Rasmus Villemoes <linux@rasmusvillemoes.dk>, Andy Shevchenko <andriy.shevchenko@linux.intel.com>, Maxim Kuvyrkov <maxim.kuvyrkov@linaro.org>, Alexey Klimov <klimov.linux@gmail.com> Subject: [PATCH 24/34] mISDN: optimize get_free_devid() Date: Sat, 18 Nov 2023 07:50:55 -0800 Message-Id: <20231118155105.25678-25-yury.norov@gmail.com> X-Mailer: git-send-email 2.40.1 In-Reply-To: <20231118155105.25678-1-yury.norov@gmail.com> References: <20231118155105.25678-1-yury.norov@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Spam-Status: No, score=-0.6 required=5.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,T_SCC_BODY_TEXT_LINE autolearn=unavailable autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on groat.vger.email Precedence: bulk List-ID: <linux-kernel.vger.kernel.org> X-Mailing-List: linux-kernel@vger.kernel.org X-Greylist: Sender passed SPF test, not delayed by milter-greylist-4.6.4 (groat.vger.email [0.0.0.0]); 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Series |
biops: add atomig find_bit() operations
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Commit Message
Yury Norov
Nov. 18, 2023, 3:50 p.m. UTC
get_free_devid() traverses each bit in device_ids in an open-coded loop.
We can do it faster by using dedicated find_and_set_bit().
It makes the whole function a nice one-liner, and because MAX_DEVICE_ID
is a small constant-time value (63), on 64-bit platforms find_and_set_bit()
call will be optimized to:
ffs();
test_and_set_bit().
Signed-off-by: Yury Norov <yury.norov@gmail.com>
---
drivers/isdn/mISDN/core.c | 9 ++-------
1 file changed, 2 insertions(+), 7 deletions(-)
diff --git a/drivers/isdn/mISDN/core.c b/drivers/isdn/mISDN/core.c index ab8513a7acd5..3f97db006cf3 100644 --- a/drivers/isdn/mISDN/core.c +++ b/drivers/isdn/mISDN/core.c @@ -197,14 +197,9 @@ get_mdevice_count(void) static int get_free_devid(void) { - u_int i; + u_int i = find_and_set_bit((u_long *)&device_ids, MAX_DEVICE_ID + 1); - for (i = 0; i <= MAX_DEVICE_ID; i++) - if (!test_and_set_bit(i, (u_long *)&device_ids)) - break; - if (i > MAX_DEVICE_ID) - return -EBUSY; - return i; + return i <= MAX_DEVICE_ID ? i : -EBUSY; } int