On 04. 03. 24, 5:37, Rengarajan.S@xxxxxxxxxxxxx wrote:
Hi Jiri,
On Fri, 2024-02-23 at 10:26 +0100, Jiri Slaby wrote:
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On 23. 02. 24, 10:21, Rengarajan.S@xxxxxxxxxxxxx wrote:
On Fri, 2024-02-23 at 07:08 +0100, Jiri Slaby wrote:
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On 22. 02. 24, 14:49, Rengarajan S wrote:
Updated the TX Burst implementation by changing the circular
buffer
processing with the pre-existing APIs in kernel. Also updated
conditional
statements and alignment issues for better readability.
Hi,
so why are you keeping the nested double loop?
Hi, in order to differentiate Burst mode handling with byte mode
had
seperate loops for both. Since, having single while loop also does
not
align with rx implementation (where we have seperate handling for
burst
and byte) have retained the double loop.
So obviously, align RX to a single loop if possible. The current TX
code
is very hard to follow and sort of unmaintainable (and buggy). And
IMO
it's unnecessary as I proposed [1]. And even if RX cannot be one
loop,
you still can make TX easy to read as the two need not be the same.
[1]
https://lore.kernel.org/all/b8325c3f-bf5b-4c55-8dce-ef395edce251@xxxxxxxxxx/
while (data_empty_count) {
cnt = CIRC_CNT_TO_END();
if (!cnt)
break;
if (cnt < UART_BURST_SIZE || (tail & 3)) { // is_unaligned()
writeb();
cnt = 1;
} else {
writel()
cnt = UART_BURST_SIZE;
}
uart_xmit_advance(cnt);
data_empty_count -= cnt;
}
With the above implementation we are observing performance drop of 2
Mbps at baud rate of 4 Mbps. The reason for this is the fact that for
each iteration we are checking if the the data need to be processed via
DWORDs or Bytes. The condition check for each iteration is causing the
drop in performance.
Hi,
the check is by several orders of magnitude faster than the I/O proper.
So I don't think that's the root cause.
With the previous implementation(with nested loops) the performance is
found to be around 4 Mbps at baud rate of 4 Mbps. In that
implementation we handle sending DWORDs continuosly until the transfer
size < 4. Can you let us know any other alternatives for the above
performance drop.
Could you attach the patch you are testing?
thanks,
--
js
suse labs
