linux-kernel - Re: [PATCH 2/3] habanalabs: trace MMU map/unmap page

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Date:   Thu, 11 Aug 2022 09:50:46 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Oded Gabbay <ogabbay@...nel.org>
Cc:     linux-kernel@...r.kernel.org, gregkh@...uxfoundation.org,
        Ohad Sharabi <osharabi@...ana.ai>
Subject: Re: [PATCH 2/3] habanalabs: trace MMU map/unmap page

On Thu, 11 Aug 2022 14:39:52 +0300
Oded Gabbay <ogabbay@...nel.org> wrote:

> @@ -259,7 +261,12 @@ int hl_mmu_unmap_page(struct hl_ctx *ctx, u64 virt_addr, u32 page_size, bool flu
>  	if (flush_pte)
>  		mmu_funcs->flush(ctx);
>  
> -	return rc;
> +	if (rc)
> +		return rc;

If you want to avoid the condition if tracing is disabled (for a
micro-optimization) you can instead do:

	if (trace_habanalabs_mmu_unmap_enabled() && !rc)
		trace_habanalabs_mmu_unmap(hdev->dev, virt_addr, 0, page_size, flush_pte);

	return rc;

This way the above trace_habanalabs_mmu_unmap_enabled() is a static_branch,
and will become a nop falling into the "return rc", and when the tracepoint
is enabled, it will jump to a compare of "!rc".

-- Steve


> +
> +	trace_habanalabs_mmu_unmap(hdev->dev, virt_addr, 0, page_size, flush_pte);
> +
> +	return 0;
>  }
>