From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from ozlabs.org (ozlabs.org [103.22.144.67]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 2C9531A05A1 for ; Mon, 22 Sep 2014 19:03:05 +1000 (EST) Message-ID: <541FDDD6.9040009@freescale.com> Date: Mon, 22 Sep 2014 11:29:10 +0300 From: Laurentiu Tudor MIME-Version: 1.0 To: Michael Neuling , , , , Subject: Re: [PATCH 03/15] powerpc/msi: Improve IRQ bitmap allocator References: <1411028820-29933-1-git-send-email-mikey@neuling.org> <1411028820-29933-4-git-send-email-mikey@neuling.org> In-Reply-To: <1411028820-29933-4-git-send-email-mikey@neuling.org> Content-Type: text/plain; charset="UTF-8" Cc: cbe-oss-dev@lists.ozlabs.org, imunsie@au.ibm.com, linux-kernel@vger.kernel.org, linuxppc-dev@ozlabs.org, anton@samba.org, jk@ozlabs.org List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Hi Michael, Minor comment inline. On 09/18/2014 11:26 AM, Michael Neuling wrote: > From: Ian Munsie > > Currently msi_bitmap_alloc_hwirqs() will round up any IRQ allocation requests > to the nearest power of 2. eg. ask for 5 IRQs and you'll get 8. This wastes a > lot of IRQs which can be a scarce resource. > > For cxl we can require multiple IRQs for every contexts that is attached to the > accelerator. For AFU directed accelerators, there may be 1000s of contexts > attached, hence we can easily run out of IRQs, especially if we are needlessly > wasting them. > > This changes the msi_bitmap_alloc_hwirqs() to allocate only the required number > of IRQs, hence avoiding this wastage. > > Signed-off-by: Ian Munsie > Signed-off-by: Michael Neuling > --- > arch/powerpc/sysdev/msi_bitmap.c | 18 +++++++++++++----- > 1 file changed, 13 insertions(+), 5 deletions(-) > > diff --git a/arch/powerpc/sysdev/msi_bitmap.c b/arch/powerpc/sysdev/msi_bitmap.c > index 2ff6302..e001559 100644 > --- a/arch/powerpc/sysdev/msi_bitmap.c > +++ b/arch/powerpc/sysdev/msi_bitmap.c > @@ -24,28 +24,36 @@ int msi_bitmap_alloc_hwirqs(struct msi_bitmap *bmp, int num) > * This is fast, but stricter than we need. We might want to add > * a fallback routine which does a linear search with no alignment. > */ Is this comment still relevant (especially the part mentioning "fast")? --- Best Regards, Laurentiu